Method of driving an electrostatic actuator

ABSTRACT

An electrostatic actuator comprises first and second movable sections and a stator. The stator has a hollow frame into which the movable sections are arranged independently. Driving electrodes are provided on surfaces of the movable sections and holding electrodes are also provided on the opposite surfaces pf the movable section. A driving electrode section is provided on the inner surface of the stator facing the driving electrodes on the movable section. Also, holding electrode sections are provided on the inner surface of the stator facing the holding electrodes on the movable section. Stripes of the electrodes are arranged in a longitudinal direction and each strip is extended in a lateral direction crossing the longitudinal direction, and the holding electrodes are extended in the longitudinal direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2000-297432, filed Sep. 28,2000, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrostatic actuator forelectrostatically driving a slider or a movable section and a method ofdriving the same, particularly, to an electrostatic actuator includingmovable sections that can be driven individually and a method of drivingthe same.

2. Description of the Related Art

An electrostatic actuator is small and lightweight and, thus, can beused for the focusing of a lens system mounted to an endoscope, amovable telephone such as a portable telephone or an apparatus such asvarious kinds of PDA (Personal Digital Assistant). Such being thesituation, the electrostatic actuator attracts attentions in recentyears.

FIG. 1 is an oblique view showing the construction of a conventionalelectrostatic actuator 100. As shown in the drawing, the electrostaticactuator 100 comprises a slider or movable section 101 and a stator 102.The movable section 101 is substantially in the form of a parallelepipedhaving a through-hole formed therein in a manner to extend in thelongitudinal direction of the movable section 101, and the stator 102 isalso substantially in the form of a parallelepiped having a through-holeformed therein in a manner to extend in the longitudinal direction ofthe stator 102. The movable section 101 is slidable into thethrough-hole of the stator 102 such that the movable section 101 ismovable within the stator 102 in the longitudinal direction of thestator 102. Incidentally, a clearance of several microns is providedbetween the stator 102 and the movable section 101.

Also, a convex stripe electrodes 103A and 103B are formed by, forexample, an etching in the movable section 101 so as to form a pair ofelectrode surfaces facing the inner surfaces of the stator 102. Anoptical system of lenses 104 having optical axes extending along theaxis of the through-hole are fixed within the through-hole of themovable section 101. The movable section 101 is moved and the opticalsystem of these lenses is also moved with the movable section 101 so asto adjust the focus of the optical system on a subject to be examined.

A wiring 105 for applying a driving signal to the movable section 101 isconnected to the movable section 101. Glass plates 106A and 106B aremounted to those inner surfaces of the stator 102 which face theelectrodes 103A and 103B, respectively, and first electrodes 107A of afirst group GA and a second group GB and second electrodes 107B of athird group GC and a fourth group GD are formed on the glass plates 106Aand 106B, respectively, by patterning a conductive material. Theelectrodes 107A of the first group GA and the second group GB arealternately arranged at the same pitch. Likewise, the electrodes 107B ofthe third group GC and the fourth group GD are also alternately arrangedin the same pitch. Also, the electrodes 107A and the electrodes 107B arearranged deviant from each other by a half pitch.

The operation of the electrostatic actuator having the constructiondescribed above will now be described with reference to FIG. 2.

(1) In the first step, a voltage of +V [V] is applied to the first groupGA of the electrode 107A. As a result, an electrostatic attracting forceis generated between the electrode 107A of the first group GA and theelectrode 103A. By this electrostatic attracting force, the movablesection 101 begins to be moved toward the glass plate 106A of the stator102, and the electrode 103A is attracted to the electrode 107A of thefirst group GA a predetermined time later.

(2) In the next step, a voltage of +V [V] is applied to the electrode107B of the third group GC among the electrodes 107B, with the resultthat an electrostatic force is generated between the electrode 107B ofthe third group GC and the electrode 103B. By this electrostatic force,the movable section 101 begins to be moved toward the glass plate 106Bof the stator 102. As a result, the electrode 103B is attracted to theelectrode 107B of the third group GC a predetermined time later. Themovable section 101 is moved to the right in FIG. 2 by a distance equalto half the arranging pitch of the electrode 106A or 106B, compared withthe position described in item (1) above.

(3) Further, a voltage of +V [V] is applied to the second group GB ofthe electrode 107A, with the result that an electrostatic force isgenerated between the electrode 107A of the second group GB and theelectrode 103A. By this electrostatic force, the movable section 101begins to be moved again toward the glass plate 106A, and the electrode103A is attracted to the electrode 107A of the second group GB apredetermined time later. The movable section 101 is moved to the rightin FIG. 2 by a distance equal to the arranging pitch of the electrode107A or 107B, compared with the position described in item (1) above.

(4) Still further, a voltage of +V [V] is applied to the fourthelectrode GD of the electrode 107B, with the result that anelectrostatic force is generated between the electrode 107B of thefourth group GD and the electrode 103B. By this electrostatic force, themovable section 101 begins to be moved again toward the glass substrate106B, and the electrode 103B is attracted to the electrode 107B of thefourth group GD. The movable section 101 is moved to the left in FIG. 2by a distance equal to 1.5 times as much as the arranging pitch of theelectrode 107A or 107B, compared with the position described in item (1)above.

The steps of items (1) to (4) described above are repeated so as to movethe movable section 101 to the right in FIG. 2 by a distance equal tohalf the arranging pitch of the electrodes every time each of the stepsof items (2) to (4) is performed.

It should also be noted that, if the voltage is applied to the electrodein the order of items (4), (3), (2) and (1) described above, the movablesection 101 can be moved to the right in FIG. 2 by a distance equal tohalf the arranging pitch of the electrodes every time each of the stepsof items (3) to (1) is performed.

It is possible to move the lens 104 mounted to the movable section 101by moving the movable section 101 by the steps of items (1) to (4)described above so as to adjust the focus of the lens 104 on thesubject.

As described above, in the conventional electrostatic actuator, it ispossible to move the movable section to a desired position so as toadjust the focus of the lens on the subject to be photographed. However,the conventional electrostatic actuator gives rise to the problem thatit is impossible to realize the zooming function of magnifying orreducing the photographed image. The difficulty is based on themechanism that the lens system is moved with a single movable section.

It should also be noted that, even if a plurality of movable sectionsare mounted to the conventional electrostatic actuator for magnifying orreducing the photographed image, it is necessary for the plural movablesections to be moved or fixed independently for magnifying or reducingthe photographed image. In the electrostatic actuator of theconventional structure, however, it is impossible to operate theelectrostatic actuator with the plural movable sections moved or fixedwithin the stator independently.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an electrostaticactuator capable of independently operating movable sections formagnifying or reducing the photographed image.

According to a first aspect of the present invention, there is providedan electrostatic actuator, comprising:

first stator electrodes arranged in a predetermined direction andextending in a direction crossing the predetermined direction;

a second stator electrode arranged to face the first stator electrodesand extending in the predetermined direction;

a third stator electrode arranged to face the first stator electrodesand extending in the predetermined direction so as to be electricallyisolated from the second stator electrode;

a first movable section provided with first and second movable sectionelectrodes, arranged movable within a moving space in the predetermineddirection, the moving space being defined between the first statorelectrodes and the second stator electrode, the first movable sectionelectrodes being mounted to the first movable section to face the firststator electrodes, and the second movable section electrode beingmounted to the first movable section to face the second statorelectrode; and

a second movable section provided with third and fourth movable sectionelectrodes, arranged independently of the first movable section, thesecond movable section being movable within the moving space in thepredetermined direction, the third movable section electrodes beingmounted to the second movable section to face the first statorelectrodes, and the fourth movable section electrode being mounted tothe second movable section to face the third stator electrode.

According to a second aspect of the present invention, there is providedan electrostatic actuator comprising:

a stator including a hollow stator frame having a space extending in apredetermined direction, the stator frame having a first inner surfaceextending in parallel to the predetermined direction and a second innersurface facing the first inner surface, first stator electrodes arrangedin the predetermined direction on the first inner surface and each ofthe stator electrode extending in a direction crossing the predetermineddirection, and second and third stator electrodes electrically isolatedeach other, arranged on the second inner surface and extending in thepredetermined direction;

a first movable section arranged in the space to be movable in thepredetermined direction, the first movable section including firstmovable section electrodes facing the first stator electrodes, each ofthe first movable section electrodes extending in a direction crossingthe predetermined direction, and a second movable section electrodeextending in the predetermined direction to face the second statorelectrode;

a second movable section arranged in the space to be movable in thepredetermined direction, and including third movable section electrodesfacing the first electrodes, each of the third movable sectionelectrodes extending in a direction crossing the predetermineddirection, and a fourth movable section electrode extending in thepredetermined direction to face the third stator electrode, and

a driving circuit configured to supply a first driving signal to thefirst stator electrodes, to supply one of a second driving signal and afirst holding voltage signal to the second stator electrode, and tosupply one of a third driving signal and a second holding voltage signalto the third stator electrode so as to move both or one of the first andsecond movable sections in the predetermined direction.

According to a third aspect of the present invention, there is providedan imaging apparatus for forming an image of a subject on animage-forming surface, comprising:

first stator electrodes arranged in a predetermined direction andextending in a direction crossing the predetermined direction;

a second stator electrode arranged to face the first stator electrodesand extending in the predetermined direction;

a third stator electrode arranged to face the first stator electrodesand extending in the predetermined direction so as to be electricallyisolated from the second stator electrode;

a first movable section having a first hollow space, provided with firstand second movable section electrodes, arranged movable within a movingspace in the predetermined direction, the moving space being definedbetween the first stator electrodes and the second stator electrode, thefirst movable section electrodes being mounted to the first movablesection to face the first stator electrodes, and the second movablesection electrode being mounted to the first movable section to face thesecond stator electrode; and

a second movable section having a second hollow space, provided withthird and fourth movable section electrodes, arranged independently ofthe first movable section, the second movable section being movablewithin the moving space in the predetermined direction, the thirdmovable section electrodes being mounted to the second movable sectionto face the first stator electrodes, and the fourth movable sectionelectrode being mounted to the second movable section to face the thirdstator electrode.

a first optical lens system having a first optical axis arranged in thepredetermined direction within the first hollow space;

a second optical system having a second optical axis arranged in thepredetermined direction within the second hollow space, the imageforming surface configured to face an image of a subject depending onthe positions of the first and second lens systems relative to theimage-forming surface; and

a driving circuit configured to supply a first driving signal to thefirst stator electrodes, to supply one of a second driving signal and afirst holding voltage signal to the second stator electrode, and tosupply one of a third driving signal and a second holding voltage signalto the third stator electrode so as to move both or one of the first andsecond movable sections in the predetermined direction.

According to a fourth aspect of the present invention, there is provideda method of driving an electrostatic actuator, the electrostaticactuator comprising:

first stator electrodes arranged in a predetermined direction andextending in a direction crossing the predetermined direction;

a second stator electrode arranged to face the first stator electrodesand extending in the predetermined direction;

a third stator electrode arranged to face the first stator electrodesand extending in the predetermined direction so as to be electricallyisolated from the second stator electrode;

a first movable section provided with first and second movable sectionelectrodes, arranged movable within a moving space in the predetermineddirection, the moving space being defined between the first statorelectrodes and the second stator electrode, the first movable sectionelectrodes being mounted to the first movable section to face the firststator electrodes, and the second movable section electrode beingmounted to the first movable section to face the second statorelectrode; and

a second movable section provided with third and fourth movable sectionelectrodes, arranged independently of the first movable section, thesecond movable section being movable within the moving space in thepredetermined direction, the third movable section electrodes beingmounted to the second movable section to face the first statorelectrodes, and the fourth movable section electrode being mounted tothe second movable section to face the third stator electrode; themethod comprising:

supplying a first driving a driving signal to the first statorelectrodes;

supplying one of a second driving voltage and a first holding voltagesignal to the second stator electrode; and

supplying one of a third driving signal and a second holding voltagesignal to the third stator electrode wherein both or one of the firstand second movable sections move in the predetermined direction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is an oblique view schematically showing a movable section and astator included in a conventional electrostatic actuator;

FIG. 2 is a vertical cross sectional view schematically showing theconstruction inside the conventional electrostatic actuator;

FIG. 3A is an oblique view schematically showing the construction of anelectrostatic actuator according to a first embodiment of the presentinvention, in which pair of movable sections is located outside of thestator frame;

FIG. 3B is an oblique view schematically showing the arrangement of thestator electrodes of the stator on the driving side shown in FIG. 3A;

FIG. 3C is an oblique view schematically showing the arrangement of thestator electrodes on the side of holding the movable section shown inFIG. 3A;

FIG. 4A is a vertical cross sectional view schematically showing theinner structure of the electrostatic actuator shown in FIG. 3A;

FIG. 4B is a cross sectional view schematically showing the constructionof the electrostatic actuator along the line X—X shown in FIG. 4A;

FIG. 4C is a cross sectional view schematically showing the constructionof the electrostatic actuator along the line Y—Y shown in FIG. 4A;

FIG. 4D is a cross sectional view schematically showing the relationshipbetween the number of holding electrodes and the side surface gap in theelectrostatic actuator shown in FIG. 4A;

FIGS. 5A to 5F are timing charts showing the voltages applied to theelectrodes of the stator in the case where two movable sections aresimultaneously moved in the same direction in the electrostatic actuatorshown in FIG. 4A;

FIGS. 6A to 6F are timing charts showing the voltages applied to theelectrodes of the stator in the case where one of two movable sectionsis moved in a certain direction in the electrostatic actuator shown inFIG. 4A;

FIGS. 7A to 7F are timing charts showing the voltages applied to theelectrodes of the stator in the case where the other of the two movablesections is moved in a certain direction in the electrostatic actuatorshown in FIG. 4A;

FIGS. 8A to 8C are cross sectional views directed to a modification ofthe electrostatic actuator shown in FIG. 4A and each showingschematically the operating states of two movable sections;

FIGS. 9A to 9F are timing charts showing the voltages applied to theelectrodes of the stator in the case where two movable sections aresimultaneously moved in the same direction in the electrostatic actuatorshown in FIG. 8A;

FIGS. 10A to 10F are timing charts showing the voltages applied to theelectrodes of the stator in the case where one of two movable sectionsis moved in a certain direction in the electrostatic actuator shown inFIG. 8B;

FIGS. 11A to 11F are timing charts showing the voltages applied to theelectrodes of the stator in the case where the other of the two movablesections is moved in a certain direction in the electrostatic actuatorshown in FIG. 8C;

FIG. 12A is a vertical cross sectional view schematically showing theinner structure of an electrostatic actuator according to a modificationof the first embodiment of the present invention;

FIG. 12B is a graph showing the relationship between the positions ofthe first and second movable sections and the optical magnification inthe electrostatic actuator shown in FIG. 12A;

FIG. 13A is a vertical cross sectional view schematically showing themovable section of an electrostatic actuator according to a modificationof a second embodiment of the present invention;

FIG. 13B is a plan view schematically showing the electrode pattern onthe lower surface of the movable section shown in FIG. 13A;

FIG. 13C is a plan view schematically showing the electrode pattern onthe glass plate of a stator of the electrostatic actuator having themovable sections shown in FIGS. 13A and 13B incorporated therein;

FIG. 14A is a vertical cross sectional view schematically showing themovable section of the electrostatic actuator according to amodification of the second embodiment of the present invention;

FIG. 14B is a plan view schematically showing the electrode pattern onthe lower surface of the movable section shown in FIG. 14A;

FIG. 14C is a plan view schematically showing the electrode pattern onthe glass plate of the stator of an electrostatic actuator having themovable sections shown in FIGS. 14A and 14B incorporated therein;

FIG. 15A is plan view schematically showing in a dismantled state themovable section of the electrostatic actuator shown in FIG. 4A;

FIG. 15B is an oblique view schematically showing the assembled state ofthe movable section shown in FIG. 15A;

FIG. 15C is a cross sectional view schematically showing the movablesection shown in FIG. 15B and a mold having the movable sectionincorporated therein;

FIG. 15D is an oblique view schematically showing the movable sectionprepared by using the mold shown in FIG. 15C;

FIG. 16A is an oblique view schematically showing in a partlyperspective fashion the mold for manufacturing the stator of theelectrostatic actuator shown in FIG. 4A;

FIG. 16B is an oblique view schematically showing a glass plate used formanufacturing the stator included in the electrostatic actuator shown inFIG. 4A;

FIG. 16C is an oblique view schematically showing in a partlyperspective fashion the assembled structure by mounting a glass plate tothe mold of the stator shown in FIG. 16A;

FIG. 16D is an oblique view schematically showing the core mounted tothe mold of the stator shown in FIG. 16C;

FIG. 17A is an oblique view schematically showing the electrode of themovable section used in the method of manufacturing the electrostaticactuator of the present invention;

FIG. 17B is an oblique view schematically showing the body of themovable section used in the method of manufacturing the electrostaticactuator of the present invention;

FIG. 17C is an oblique view schematically showing the movable sectionprepared by fixing the electrode of the movable section shown in FIG.17A to the body of the movable section shown in FIG. 17B;

FIG. 18 is a vertical cross sectional view schematically showing themovable section used in the manufacturing method of an electrostaticactuator of the present invention and a mold of the movable section; and

FIG. 19 is a plan view schematically showing a mold of the movablesection and the stator used in the manufacturing method of anelectrostatic actuator of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Electrostatic actuators according to some embodiments of the presentinvention will now be described with reference to the accompanyingdrawings.

The electrostatic actuator, which is small and lightweight, can be usedfor the focusing of the lens mounted to an endoscope, a movabletelephone such as a portable telephone and various PDA's (PersonalDigital Assistants) and, thus, attracts attentions in recent years.

FIGS. 3A to 4A collectively show an electrostatic actuator according toa first embodiment of the present invention.

FIG. 3A is an oblique view schematically showing the electrostaticactuator 1 according to the first embodiment of the present invention.The electrostatic actuator 1 shown in FIG. 3A comprises first and secondmovable sections 2A and 2B having a pair of movable section electrodes4, 8 and another pair of movable section electrodes 5, 11 formed on theupper surfaces and the lower surfaces, respectively, and a stator 3having a pair of stator electrode sections 12, 14 arranged to face themovable section electrodes 4, 8 on the upper surfaces and the movablesection electrodes 5, 11 on the lower surfaces of the movable sections2A, 2B, respectively.

The movable section electrodes 4, 8, 5, 11 are grouped into drivingelectrodes 4, 8 for driving the movable sections 2A, 2B and the holdingelectrodes 5, 11 for fixing the movable sections 2A, 2B. On the otherhand, the stator electrode sections 12, 14 are grouped into a drivingelectrode 12 for driving the stator and a holding electrode 14 forholding the movable sections 2A, 2B at the desired positions.

The construction of the stator 3 will now be described. Specifically,the stator 3 is formed of a stator frame 3A formed of a frame of ahollow cube having a through-hole formed therein. The stator frame 3Ahas an upper inner surface 3A-1, a lower inner surface 3A-2, and sideinner surfaces 3A-3 and 3A-4.

A driving electrode section 12 for driving the movable sections 2A, 2Bis formed on one inner surface of the stator frame 3A, e.g., on theupper inner surface 3A-1. Further, a holding electrode section 14 forholding the movable sections 2A, 2B at the desired positions is formedon another inner surface facing the upper inner surface of the statorframe 3A, e.g., on the lower inner surface 3A-2.

The driving electrode section 12 is patterned in a desired shape andformed on the surface of a glass plate 13 in a manner to form aplurality of electrode stripes extending in, for example, the directionperpendicular to the longitudinal direction of the stator 3, i.e.,extending in the lateral direction of the stator 3, as shown in FIG. 3A.Incidentally, the glass plate 13 having the driving electrode section 12formed thereon is fitted to the inner surface 3A-1 of the stator 3.Also, each of the electrode stripes 12A to 12D of the driving electrodesection 12 has a width of about 20 μm. Also, the clearance between theadjacent electrode stripes of the electrode stripes 12A to 12D of thedriving electrode section 12 is about 20 μm, and the electrode stripes12A to 12D are arranged at a pitch of about 40 μm.

A holding electrode section 14 is formed on the inner surface 3A-2 ofthe stator frame 3A facing the driving electrode section 12. The holdingelectrode section 14 is patterned in a desired shape and formed in apredetermined direction on the surface of a glass plate 15. The glassplate 15 having the holding electrode formed thereon is fitted to theinner surface 3A-2 of the stator 3. It should be noted that 5 electrodestripes are formed in parallel in the holding electrode section 14 in amanner to correspond to 3 holding electrodes 5 on the side of themovable section of a first movable section 2A referred to herein laterand 2 holding electrodes 11 on the side of the movable section of asecond movable section 2B referred to herein later. The 5 holdingelectrode section 14 shown in FIG. 3A are arranged apart from each otherin substantially the entire region including the central region on theglass substrate 15. The holding electrode sections 14A corresponding tothe fixing electrode 5 on the side of the movable section areelectrically connected at the edge portion of the glass plate 15 in oneof the side regions in the longitudinal direction of the glass plate 15,and the 2 holding electrode sections 14B corresponding to the fixingelectrode 11 on the side of the movable section are electricallyconnected in the other side regions in the longitudinal direction on theglass plate 15. What should be noted is that the holding electrodesections 14A and 14B are arranged electrically independently so as tocontrol independently the first and second movable sections 2A, 2B.

Stoppers 16 are formed on the side inner surfaces 3A-3, 3A-4 of thestator frame 3A for preventing the side surfaces of the first and secondmovable sections 2A, 2B from contacting directly the side inner surfaces3A-3, 3A-4. Similarly, stoppers (not shown) are formed on the innersurfaces 3A-1, 3A-2 for preventing the movable sections 2A, 2B frombeing brought into direct contact with the driving electrodes 12, 14.

The construction of each of the two movable sections 2A, 2B will now bedescribed in detail.

Specifically, the first movable section 2A comprises a substantiallyparallelepiped hollow support body formed of an electric conductivemember, the electrodes 4, 5 formed on the outer surfaces of the hollowsupport body, a lens 6 arranged in the hollow portion of the supportbody, and a wiring 7 for removing the electric charge from the supportbody. Likewise, the second movable section 2B comprises a substantiallyparallelepiped hollow support body formed of an electric conductivemember, the electrodes 8, 11 formed on the outer surfaces of the hollowsupport body, a lens 9 arranged in the hollow portion of the supportbody, and a wiring 10 for removing the electric charge from the supportbody. The support body and electrodes 4, 5 may be formed into a unitaryconfiguration.

The first movable section 2A and the second movable section 2B areinserted apart from each other into the through-hole of the support bodysuch that these first and second movable sections 2A and 2B are movablein a predetermined direction.

A driving electrode 4 on the side of the movable section is formed on asurface of the first movable section 2A facing the driving electrodesection 12 on the side of the stator, e.g., on the upper surface of thefirst movable section 2A. Likewise, a fixing electrode 5 on the side ofthe movable section is formed on a surface of the first movable section2A facing the holding electrode section 14, e.g., on the lower surfaceof the first movable electrode 2A. The driving electrode 4 on the sideof the movable section is formed by etching in the form of a pluralityof projecting stripes extending in a direction perpendicular to themoving direction and arranged in the longitudinal direction. Also, thefixing electrode 5 on the side of the movable section is formed byetching in the form of a plurality of projecting stripes extending inthe moving direction and arranged in the lateral direction. The drivingelectrode 4 on the side of the movable section is formed to compriseconcave portions and convex portions with a clearance of about 20 μmprovided between the adjacent concave and convex portions. The height ofthe convex portion from the surface inside the concave portion is about10 μm. In other words, the edge surface of the convex portion of thedriving electrode 4 on the side of the movable section has a width equalto the width of one of the electrodes 12A to 12D of the drivingelectrode section 12. Also, the bottom surface of the concave portion ofthe driving electrode 4 on the side of the movable section has a widthequal to the clearance between the adjacent electrodes 12A to 12D. Theconcave or convex portions of the driving electrode 4 on the side of themovable section 4 arranged at a pitch of about 40 μm.

In the actuator shown in FIG. 3A, three holding electrodes 5 extendingin the longitudinal direction and arranged in the lateral direction aremounted to the first movable section 2A. Also, a plurality of lenses 6having aligned optical axes are fixed within the through-hole of thefirst movable section 2A.

A driving electrode 8 on the side of the movable section having a shapeand a dimension equal to those of the driving electrode 4 on the side ofthe movable section of the first movable section 2A is mounted to thesecond movable section 2B. Also, a lens 9 similar to the lens 6 is fixedwithin the through-hole of the second movable section 2B. The lenssystem formed by the lenses 6 and 9 is zoomed between the wide-angle andtelephoto lens systems by changing the arrangement of the lenses 6 and 9so as to adjust the focus on the subject in accordance with the zoomedfocal length. Two holding electrodes 11 extending in the longitudinaldirection and arranged in the lateral direction are mounted to thesecond movable section 2B. The holding electrodes 11 are formed byetching.

As apparent from the above description, the driving electrodes 4, 8 onthe side of the movable section are formed such that the concave andconvex portions of these driving electrodes 4, 8 are substantiallyparallel to each other. The holding electrodes 5, 11 on the side of themovable section are also formed such that the concave and convexportions thereof are substantially parallel to each other. The extendingdirections of the driving electrodes 4, 8 on the side of the movablesection are allowed to cross the extending directions of the holdingelectrodes 5, 11 on the side of the movable section. Also, the holdingelectrodes 5, 11 on the side of the movable section extend in thelongitudinal direction and are arranged in parallel such that theseholding electrodes 5, 11 do not overlap with other in the lateraldirection.

The first and second movable sections 2A, 2B are arranged in the movingdirection, i.e., in the longitudinal direction, and are independentlymovable in the longitudinal direction.

The operation of the actuator of the particular construction will now bedescribed with reference to FIGS. 4A to 4D. FIG. 4A is a cross sectionalview showing the state that the first and second movable sections 2A, 2Bare inserted into the through-hole of the stator frame 3A. FIG. 4B is alateral cross sectional view along the lines X—X as viewed in thedirection denoted by an arrow. Further, FIG. 4C is a lateral crosssectional view along the line Y—Y as viewed in the direction denoted byan arrow.

The driving electrode section 12 is formed of a plurality of electrodegroups each consisting of electrodes 12A to 12D of 4 phases arranged inthe moving direction, as shown in FIG. 4A. These driving electrodes 12Ato 12D are connected to a control unit 19 so as to be driven uponreceipt of control voltage signals from the control unit 19. To be morespecific, the groups of the driving electrodes 12A to 12D aresequentially arranged in the longitudinal direction, and each of thedriving electrodes 12A to 12D are commonly connected to thecorresponding driving electrode and connected to the control unit 19,and a voltage signal is applied independently to the driving electrodestripes 12A to 12D of each group. For example, where voltage is appliedto the driving electrode 12A, a voltage signal is applied to the convexportion corresponding to the driving electrode 12A of all the groups ofthe electrode section 12.

As shown in FIG. 4D, it is necessary for the width Wm of the fixingelectrode 5 or 11 of the movable section 2A or 2B and the width Ws ofthe fixing electrode 14 of the stator 3 to be set larger than theallowable moving length ΔL even if the movable section 2A or 2B is movedin the lateral direction within the frame of the stator 3. The allowablemoving length ΔL corresponds to a difference between the distance Lsbetween the stoppers, and the width Lm of the movable section 2A or 2B.The allowable moving length ΔL is produced in the actuator when themovable section 2A or 2B abuts against a stopper 16 mounted to the sidesurface of one of the stator 5 or 11 and the stopper mounted to one sidesurface of the stator 5 or 11. In the present invention, each of Wm andWs is set larger than the allowable moving length ΔL. Difficulties aregenerated if this requirement is not satisfied. Specifically, if themovable section is moved sideward by the moving length ΔL, the mutuallyfacing electrodes 5 and 14 are deviated from each other. Also, if theoverlapping area is made extremely small, the force to fix the movablesection 2A ceases to be generated.

Also, the free space between adjacent electrodes 5, adjacent electrodes11 or adjacent electrodes 14 must be greater than the moving length ΔL.If the number of holding electrodes is increased, the portion where theelectrode is not mounted is also increased. This is a disadvantageouscondition for generating an attractive force.

It should also be noted that, if the movable sections 2A, 2B have asingle electrode 5 and a single electrode 11 respectively, the singleelectrodes can not be symmetrically arranged in respect to a movingdirection of the movable section 2A, 2B so that the movable sections 2A,2B tend to be moved unstable in the driving step. It follows that it isnecessary to mount at least two electrodes to each of the movablesections 2A and 2B.

Such being the situation, in a small actuator having, for example, twosystems of stator electrodes as the holding electrodes, it is desirableto employ a combination that two electrodes are mounted to one of themovable sections 2A, 2B and three electrodes are mounted to the other ofthe movable sections 2A, 2B or another combination that three electrodesare mounted to one of the movable sections 2A, 2B and four electrodesare mounted to the other of the two movable sections 2A, 2B.

There are four operation modes in the first and second movable sections2A, 2B. Each of these operation modes will now be described.

(I) Where each of the first and second movable sections 2A and 2B ismoved to the right in FIG. 4A (hereinafter referred to as mode I):

This operation corresponds to the focusing mode in which the focus ofthe lens system is aligned on the subject.

(II) Where each of the first and second movable sections 2A and 2B ismoved to the left in FIG. 4A (hereinafter referred to as mode II):

This operation also corresponds to the focusing mode in which the focusof the lens system is aligned on the subject.

(III) Where the first movable section 2A is held stationary and thesecond movable section 2B alone is moved to the left or to the right inFIG. 4A (hereinafter referred to as operation mode III):

This operation corresponds to the zooming mode in which the lens systemis switched to the telephoto side or the wide-angle side.

(IV) Where the second movable section 2B is held stationary and thefirst movable section 2A alone is moved to the left or to the right inFIG. 4A (hereinafter referred to as operation mode IV):

This operation corresponds to the zooming mode in which the lens systemis switched to the telephoto side or the wide-angle side.

The four operation modes summarized above will now be described indetail.

(I) Operation mode I in which the first and second movable sections 2Aand 2B are moved to the right in FIG. 4A is performed as follows:

(1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are kept connected to the ground. Under this condition,a voltage H is applied to the driving electrodes 12A as shown in FIG.5A. As a result, the driving electrodes 4, 8 on the side of the movablesection in the vicinity of the driving electrode 12A are attracted bythe electrostatic force toward the driving electrode 12A, with theresult that the driving electrodes 4, 8 on the side of the movablesection are attracted to the driving electrode 12A. It follows that thefirst and second movable sections 2A, 2B are moved toward the glassplate 13.

(2) In the next step, the voltage of the driving electrode 12A ischanged into a low level L at time t1, and a voltage H is applied to theholding electrode sections 14A, 14B as shown in FIGS. 5E and 5F. As aresult, a strong electrostatic force is generated between the holdingelectrode section 14A and the fixing electrode 5 on the side of themovable section so as to permit the first movable section 2A to be movedtoward the glass plate 15. It follows that the fixing electrode 5 on theside of the movable section is attracted to the holding electrodesection 14A. Also, a strong electrostatic force is generated between theholding electrode section 14B and the fixing electrode 11 on the side ofthe movable section. As a result, the second movable section 2B is movedtoward the glass plate 15 so as to permit the fixing electrode 11 on theside of the movable section to be attracted to the holding electrodesection 14B.

(3) In the next step, voltage of the holding electrode sections 14A, 14Bis changed into a low level L at time t2, with the result that a voltageH is applied to the driving electrode 12B as shown in FIG. 5B. As aresult, the driving electrodes 4, 8 on the side of the movable sectionin the vicinity of the driving electrode 12B is attracted by anelectrostatic force toward the driving electrode 12B, with the resultthat the driving electrodes 4, 8 on the side of the movable section areattracted to the driving electrode 12B. It follows that the first andsecond movable electrodes 2A, 2B are moved toward the glass plate 13. Inthis step, the first and second movable sections 2A, 2B are moved to theright in FIG. 4A by a distance equal to one stripe of the drivingelectrode section 12, i.e., a distance equal to one pitch, compared withthe position described in item (1) above.

(4) In the next step, voltage of the driving electrode 12B is changed toa low level L at time t3, with the result that a voltage H is appliedagain to the holding electrode sections 14A, 14B, as shown in FIGS. 5Eand 5F, so as to generate a strong electrostatic force between theholding electrode section 14A and the fixing electrode 5 on the side ofthe movable section. It follows that the first movable section 2A ismoved toward the glass plate 15 and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section is attracted to the holding electrode section 14B.

(5) Further, the voltage of the holding electrode sections 14A, 14B ischanged into a low level L at time t4, with the result that a voltage isapplied to the driving electrode 12C, as shown in FIG. 5C. In this case,the driving electrodes 4, 8 on the side of the movable section in thevicinity of the driving electrode 12C are attracted by an electrostaticforce toward the driving electrode 12C such that the driving electrodes4, 8 on the side of the movable section are attracted to the drivingelectrode 12C. As a result, the first and second movable sections 2A, 2Bare moved toward the glass plate 13. In this case, the first and secondmovable sections 2A, 2B are moved to the right in FIG. 4A by a distanceequal to two stripes of the driving electrode section 12, i.e., adistance equal to two pitches, compared with the position described initem (1) above.

(6) In the next step, voltage of the driving electrode 12C is changed toa low level L at time t5, with the result that a voltage is appliedagain to the holding electrode sections 14A, 14B, as shown in FIGS. 5Eand 5F, so as to generate a strong electrostatic force between theholding electrode section 14A and the fixing electrode 5 on the side ofthe movable section. It follows that the first movable section 2A ismoved toward the glass plate 15 and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section is attracted to the holding electrode section 14B.

(7) In the next step, the voltage of the holding electrode sections 14A,14B is changed into a low level L at time t6, with the result that avoltage is applied to the driving electrode 12D, as shown in FIG. 5D. Inthis case, the driving electrodes 4, 8 on the side of the movablesection in the vicinity of the driving electrode 12D are attracted by anelectrostatic force toward the driving electrode 12D such that thedriving electrodes 4, 8 on the side of the movable section are attractedto the driving electrode 12D. As a result, the first and second movablesections 2A, 2B are moved toward the glass plate 13. In this case, thefirst and second movable sections 2A, 2B are moved to the right in FIG.4A by a distance equal to three stripes of the driving electrode section12, i.e., a distance equal to three pitches, compared with the positiondescribed in item (1) above.

(8) In the next step, voltage of the driving electrode 12D is changed toa low level L at time t7, with the result that a voltage is appliedagain to the holding electrode sections 14A, 14B, as shown in FIGS. 5Eand 5F, so as to generate a strong electrostatic force between theholding electrode section 14A and the fixing electrode 5 on the side ofthe movable section. It follows that the first movable section 2A ismoved toward the glass plate 15 and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section is attracted to the holding electrode section 14B.

(9) Further, the voltage of the holding electrode sections 14A, 14B ischanged into a low level L at time t8, with the result that a voltage isapplied to the driving electrode section 12A, as shown in FIG. 5A. Inthis case, the driving electrodes 4, 8 on the side of the movablesection in the vicinity of the driving electrode section 12A areattracted by an electrostatic force toward the driving electrode section12A such that the driving electrodes 4, 8 on the side of the movablesection are attracted to the driving electrode 12C. As a result, thefirst and second movable sections 2A, 2B are moved toward the glassplate 13. In this case, the first and second movable sections 2A, 2B aremoved to the right in FIG. 4A by a distance equal to four stripes of thedriving electrode section 12, i.e., a distance equal to four pitches,compared with the position described in item (1) above.

The steps of items (1) to (9) described above are repeated until thefirst and second movable sections 2A, 2B are moved by a desireddistance.

(II) Operation mode II in which the first and second movable sections2A, 2B are both moved to the left in FIG. 4A will now be described.

The first and second movable sections 2A, 2B can be moved to the left inFIG. 4A if the steps for operation mode I described above are carriedout in the opposite direction. To be more specific, the first and secondmovable sections 2A, 2B can be moved to the right left in FIG. 4A byrepeating the steps for operation mode I in the order of steps (9), (8),(7), (6), (5), (4), (3), (2) and (1). Of course, the number ofrepetitions is determined in accordance with the desired distance ofmovement of the first and second movable sections 2A, 2B.

It should be noted that each of operation modes I and II is an operationof the focusing mode for aligning the focus on the subject. Whether toemploy operation mode I or II is determined appropriately depending onthe initial positions of the first and second movable sections 2A, 2Band on the direction of the movement of the first and second movablesections 2A, 2B which permits achieving the focusing in a shorter time.

(III) Operation mode III in which the first movable section 2A is heldstationary and the second movable section 2B alone is moved to the leftor to the right in FIG. 4A will now be described.

Let us describe first the case where the second movable section 2B ismoved to the right in FIG. 4A.

(1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are kept connected to the ground as in operation mode Idescribed previously. Then, a voltage is applied to the holdingelectrode section 14B as shown in FIG. 6F. As a result, an electrostaticforce is generated between the holding electrode section 14B and thefixing electrode 5 on the side of the movable section. It follows thatthe second movable section 2B is moved toward the glass plate 15, andthe fixing electrode 5 on the side of the movable section is attractedto the holding electrode section 14B. Where voltage is applied to theholding electrode section 14A as shown in FIG. 6E, the first movablesection 2A is attracted to and fixed temporarily to the glass plate 15.

(2) In the next step, a voltage H is applied to the driving electrode12A at time t1 as shown in FIG. 6A, with the voltage H kept applied tothe holding electrode section 14A as shown in FIG. 6E. As a result, thedriving electrode 8 on the side of the movable section 2B in thevicinity of the driving electrode 12A is attracted by an electrostaticforce, with the result that the driving electrode 8 on the side of themovable section 2B is attracted to the driving electrode 12A. It followsthat the second movable section 2B is moved toward the glass plate 13.On the other hand, since the voltage H is kept applied to the holdingelectrode section 14A, the first movable section 2A is kept fixed on theside of the glass plate 15.

(3) In the next step, a voltage H is applied to the holding electrodesection 14B at time t2 as shown in FIG. 6F, with voltage kept applied tothe holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section. As aresult, the second movable section 2B is moved toward the glass plate15, and the fixing electrode 11 on the side of the movable section 2B isattracted to the holding electrode section 14B.

(4) In the next step, a voltage H is applied to the driving electrode12B at time t3 as shown in FIG. 6B with the voltage kept applied to theholding electrode section 14A. As a result, the driving electrode 8 onthe side of the movable section 2B in the vicinity of the drivingelectrode 12B is attracted toward the driving electrode 12B by anelectrostatic force, and the driving electrode 8 on the side of themovable section 2B is attracted to the driving electrode 12B. It followsthat the second movable section 2B is moved toward the glass plate 13.On the other hand, the first movable section 2A is similarly kept fixedon the side of the glass plate 15. In this case, the second movablesection 2B is moved to the right in FIG. 4A by a distance equal to onestripe of the driving electrode section 12, i.e., a distance equal toone pitch, compared with the position described in item (1) above.

(5) In the next step, a voltage H is applied to the holding electrodesection 14B at time t4 as shown in FIG. 6F, with voltage kept applied tothe holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section 2B.As a result, the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable sectionis attracted to the holding electrode section 14B.

(6) In the next step, a voltage is applied to the driving electrode 12Cat time t5 as shown in FIG. 6C with the voltage kept applied to theholding electrode section 14A. As a result, the driving electrode 8 onthe side of the movable section 2B in the vicinity of the drivingelectrode 12C is attracted toward the driving electrode 12C by anelectrostatic force, and the driving electrode 8 on the side of themovable section is attracted to the driving electrode 12C. It followsthat the second movable section 2B is moved toward the glass plate 13.On the other hand, the first movable section 2A is similarly kept fixedon the side of the glass plate 15. In this case, the second movablesection 2B is moved to the right in FIG. 4A by a distance equal to twostripes of the driving electrode section 12, i.e., a distance equal totwo pitches, compared with the position described in item (1) above.

(7) In the next step, a voltage H is applied to the holding electrodesection 14B at time t6 as shown in FIG. 6F, with voltage kept applied tothe holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section 2B.As a result, the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable section2B is attracted to the holding electrode section 14B.

(8) In the next step, a voltage is applied to the driving electrodestripe 12D at time t7 as shown in FIG. 6D with the voltage kept appliedto the holding electrode section 14A. As a result, the driving electrode8 on the side of the movable section 2B in the vicinity of the drivingelectrode stripe 12D is attracted toward the driving electrode section12D by an electrostatic force, and the driving electrode 8 on the sideof the movable section 2B is attracted to the driving electrode section12D. It follows that the second movable section 2B is moved toward theglass plate 13. On the other hand, the first movable section 2A issimilarly kept fixed on the side of the glass plate 15. In this case,the second movable section 2B is moved to the right in FIG. 4A by adistance equal to three stripes of the driving electrode section 12,i.e., a distance equal to three pitches, compared with the positiondescribed in item (1) above.

(9) In the next step, a voltage is applied to the holding electrodesection 14B at time t8 as shown in FIG. 6F, with voltage kept applied tothe holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section. As aresult, the second movable section 2B is moved toward the glass plate15, and the fixing electrode 11 on the side of the movable section isattracted to the holding electrode section 14B.

(10) In the next step, a voltage is applied to the driving electrode 12Aat time t9 as shown in FIG. 6A with the voltage kept applied to theholding electrode section 14A. As a result, the driving electrode 8 onthe side of the movable section in the vicinity of the driving electrode12A is attracted toward the driving electrode section 12A by anelectrostatic force, and the driving electrode 8 on the side of themovable section is attracted to the driving electrode 12A. It followsthat the second movable section 2B is moved toward the glass plate 13.On the other hand, the first movable section 2A is similarly kept fixedon the side of the glass plate 15. In this case, the second movablesection 2B is moved to the right in FIG. 4A by a distance equal to fourstripes of the driving electrode section 12, i.e., a distance equal tofour pitches, compared with the position described in item (1) above.

The steps of items (1) to (10) described above are repeated until thesecond movable section 2B is moved by a desired distance.

Also, where it is intended to move the second movable section 2B to theleft in FIG. 4A, the steps of items (1), (10), (9), (8), (7), (6), (5),(4), (3) and (2) in the operation mode III described above are repeatedin the order mentioned so as to move the second movable section 2B by adesired distance.

(IV) Operation mode IV in which the second movable section 2B is heldstationary and the first movable section 2A alone is moved to the leftor to the right in FIG. 4A will now be described.

Let us describe first the case where the first movable section 2A ismoved to the right in FIG. 4A.

(1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are kept connected to the ground as in operation mode Idescribed previously. Then, a voltage H is applied to the holdingelectrode section 14A as shown in FIG. 7E. As a result, an electrostaticforce is generated between the holding electrode section 14A and thefixing electrode 11 on the side of the movable section. It follows thatthe first movable section 2A is moved toward the glass plate 15, and thefixing electrode 5 on the side of the movable section 2A is attracted tothe holding electrode section 14A. Where voltage is applied to theholding electrode section 14B as shown in FIG. 7F, the second movablesection 2B is attracted to and fixed to the glass plate 15.

(2) In the next step, a voltage H is applied to the driving electrode12A at time t1 as shown in FIG. 7A, with the voltage H kept applied tothe holding electrode section 14B as shown in FIG. 7F. As a result, thedriving electrode 4 on the side of the movable section 2A in thevicinity of the driving electrode 12A is attracted by an electrostaticforce to the driving electrode 12A, with the result that the drivingelectrode 4 on the side of the movable section 2A is attracted to thedriving electrode 12A. It follows that the first movable section 2A ismoved toward the glass plate 13. On the other hand, since the voltage His kept applied to the holding electrode section 14B, the second movablesection 2B is kept fixed on the side of the glass plate 15.

(3) In the next step, a voltage H is applied to the holding electrodesection 14A at time t2 as shown in FIG. 7F, with voltage kept applied tothe holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section 2A. Asa result, the first movable section 2A is moved toward the glass plate15, and the fixing electrode 5 on the side of the movable section 2A isattracted to the holding electrode section 14A.

(4) In the next step, a voltage H is applied to the driving electrode12B at time t3 as shown in FIG. 7B with the voltage kept applied to theholding electrode section 14B. As a result, the driving electrode 4 onthe side of the movable section 2A in the vicinity of the drivingelectrode 12B is attracted toward the driving electrode 12B by anelectrostatic force, and the driving electrode 4 on the side of themovable section 2A is attracted to the driving electrode 12B. It followsthat the first movable section 2A is moved toward the glass plate 13. Onthe other hand, the second movable section 2B is similarly kept fixed onthe side of the glass plate 15. In this case, the first movable section2A is moved to the right in FIG. 4A by a distance equal to one stripe ofthe driving electrode section 12, i.e., a distance equal to one pitch,compared with the position described in item (1) above.

(5) In the next step, a voltage H is applied to the holding electrodesection 14A at time t4 as shown in FIG. 7E, with voltage kept applied tothe holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section 2A. Asa result, the first movable section 2A is moved toward the glass plate15, and the fixing electrode 5 on the side of the movable section 2A isattracted to the holding electrode section 14A.

(6) In the next step, a voltage H is applied to the driving electrode12C at time t5 as shown in FIG. 7C with the voltage kept applied to theholding electrode section 14B. As a result, the driving electrode 4 onthe side of the movable section 2A in the vicinity of the drivingelectrode 12C is attracted toward the driving electrode 12C by anelectrostatic force, and the driving electrode 4 on the side of themovable section 2A is attracted to the driving electrode 12C. It followsthat the first movable section 2A is moved toward the glass plate 13. Onthe other hand, the second movable section 2B is similarly kept fixed onthe side of the glass plate 15. In this case, the first movable section2A is moved to the right in FIG. 4A by a distance equal to two stripesof the driving electrode section 12, i.e., a distance equal to twopitches, compared with the position described in item (1) above.

(7) In the next step, a voltage H is applied to the holding electrodesection 14A at time t6 as shown in FIG. 7E, with voltage kept applied tothe holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section 2A. Asa result, the first movable section 2A is moved toward the glass plate15, and the fixing electrode 5 on the side of the movable section isattracted to the holding electrode section 14A.

(8) In the next step, a voltage H is applied to the driving electrodestripe 12D at time t7 as shown in FIG. 7D with the voltage kept appliedto the holding electrode section 14B. As a result, the driving electrode4 on the side of the movable section 2A in the vicinity of the drivingelectrode stripe 12D is attracted toward the driving electrode section12D by an electrostatic force, and the driving electrode 4 on the sideof the movable section 2A is attracted to the driving electrode section12D. It follows that the first movable section 2A is moved toward theglass plate 13. On the other hand, the second movable section 2B issimilarly kept fixed temporarily on the side of the glass plate 15. Inthis case, the first movable section 2A is moved to the right in FIG. 4Aby a distance equal to three stripes of the driving electrode section12, i.e., a distance equal to three pitches, compared with the positiondescribed in item (1) above.

(9) In the next step, a voltage H is applied to the holding electrodesection 14A at time t8 as shown in FIG. 7E, with voltage kept applied tothe holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section. As aresult, the first movable section 2A is moved toward the glass plate 15,and the fixing electrode 5 on the side of the movable section 2A isattracted to the holding electrode section 14A.

(10) In the next step, a voltage H is applied to the driving electrode12A at time t9 as shown in FIG. 7A with the voltage kept applied to theholding electrode section 14B. As a result, the driving electrode 4 onthe side of the movable section 2A in the vicinity of the drivingelectrode 12A is attracted toward the driving electrode section 12A byan electrostatic force, and the driving electrode 4 on the side of themovable section 2A is attracted to the driving electrode 2A. It followsthat the first movable section 2A is moved toward the glass plate 13. Onthe other hand, the second movable section 2B is temporarily kept fixedon the side of the glass plate 15. In this case, the first movablesection 2A is moved to the right in FIG. 4A by a distance equal to fourstripes of the driving electrode section 12, i.e., a distance equal tofour pitches, compared with the position described in item (1) above.

The steps of items (1) to (10) described above are repeated until thefirst movable section 2A is moved by a desired distance.

Also, where it is intended to move the first movable section 2A to theleft in FIG. 4A, the steps of items (1), (10), (9), (8), (7), (6), (5),(4), (3) and (2) in the operation mode III described above are repeatedin the order mentioned so as to move the first movable section 2A by adesired distance.

It should be noted that each of operation modes III and IV is anoperation for magnifying or reducing the photographed image. Whether toemploy operation mode III or IV is determined appropriately depending onthe initial positions of the first and second movable sections 2A, 2Band on the direction of the movement of the first and second movablesections 2A, 2B which permits achieving the magnification or reductionin a shorter time.

Incidentally, FIG. 4B shows that the first movable section 2A is movedtoward the glass plate 13, and FIG. 4C shows that the second movablesection 2B is moved toward the glass plate 15.

In the actuator shown in FIG. 4A, each of the driving electrodes 12A to12D of the driving electrode section 12 is set substantially equal tothe width of each of the driving electrodes 4 and 8 on the side of themovable section and the arranging pitch of these driving electrodes 12Ato 12D is set constant. As a modification of the actuator, it ispossible for each of the driving electrodes 12A to 12D of the drivingelectrode section 12 to be set not larger than ½ of the width of each ofthe driving electrodes 4 and 8 on the side of the movable section andfor the arranging pitch of the driving electrodes 12A to 12D to be setat ¼ of that of each of the driving electrodes 4 and 8 on the side ofthe movable section, as shown in. FIGS. 8A to 8C. In the actuator of theparticular construction, if the movable sections 2A, 2B are attractedtoward the driving electrodes 12A to 12D of the driving electrodesection 12, each of the driving electrodes 4 and 8 on the side of themovable section is allowed to face two of the driving electrodes 12A to12D, as shown in FIGS. 8A to 8C.

The operation of the actuator shown in FIGS. 8A to 8C will now bedescribed with reference to FIGS. 9A to 9F, FIGS. 10A to 10F and FIGS.11A to 11F.

(I) Operation mode I in which the first and second movable sections 2A,2B are simultaneously moved to the right as shown in FIG. 5A isperformed as follows.

(1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are held connected to the ground. Under this condition,a voltage H is applied to the driving electrodes 12A and 12B as shown inFIGS. 9A and 9B. As a result, the driving electrodes 4, 8 on the side ofthe movable sections in the vicinity of the driving electrodes 12A, 12Bare attracted toward the driving electrodes 12A, 12B by an electrostaticforce, with the result that the driving electrodes 4, 8 on the side ofthe movable sections are attracted to the driving electrode 12A. Itfollows that the first and second movable sections 2A, 2B are movedtoward the glass plate 13.

(2) In the next step, the voltage of the driving electrodes 12A and 12Bis changed into a low level at time t1 as shown in FIGS. 9A and 9B, anda voltage H is applied to the holding electrodes sections 14A, 14B asshown in FIGS. 9E and 9F. It follows that a strong electrostatic forceis generated between the holding electrode section 14A and the fixingelectrode 5 on the side of the movable section 2A. As a result, thefirst movable section 2A is moved toward the glass plate 15, and thefixing electrode 5 on the side of the movable section 2A is attracted tothe holding electrode section 14A. Also, a strong electrostatic force isgenerated between the holding electrode section 14B and the fixingelectrode 11 on the side of the movable section 2B. As a result, thesecond movable section 2B is moved toward the glass plate 15, and thefixing electrode 11 on the side of the movable section is attracted tothe holding electrode section 14B.

(3) In the next step, the voltage of the holding electrode sections 14A,14B is changed into a low level L at time t2 as shown in FIGS. 9E and9F, and a voltage H is applied to the driving electrodes 12B and 12C asshown in FIGS. 9B and 9C. As a result, the driving electrodes 4, 8 onthe side of the movable sections 2A, 2B in the vicinity of the drivingelectrodes 12B, 12C are attracted toward the driving electrodes 12B, 12Cby an electrostatic force, and the driving electrodes 4, 8 on the sideof the movable sections 2A, 2B are attracted to the driving electrodes12B, 12C. It follows that the first and second movable sections 2A, 2Bare moved toward the glass plate 13. In this case, the first and secondmovable sections 2A, 2B are moved to the right in FIG. 8A by a distanceequal to one stripe of the driving electrode section 12, i.e., adistance equal to one pitch, compared with the position described initem (1) above.

(4) In the next step, the voltage of the driving electrodes 12B and 12Cis changed into a low level L at time t3, and a voltage H is appliedagain to the holding electrodes sections 14A, 14B as shown in FIGS. 9Eand 9F. It follows that a strong electrostatic force is generatedbetween the holding electrode section 14A and the fixing electrode 5 onthe side of the movable section 2A. As a result, the first movablesection 2A is moved toward the glass plate 15, and the fixing electrode5 on the side of the movable section 2A is attracted to the holdingelectrode section 14A. Also, a strong electrostatic force is generatedbetween the holding electrode section 14B and the fixing electrode 11 ohthe side of the movable section 2B. As a result, the second movablesection 2B is moved toward the glass plate 15, and the fixing electrode11 on the side of the movable section 2B is attracted to the holdingelectrode section 14B.

(5) Further, the voltage of the holding electrode sections 14A, 14B ischanged into a low level L at time t4, and a voltage is applied to thedriving electrodes 12C and 12D as shown in FIGS. 9C and 9D. As a result,the driving electrodes 4, 8 on the side of the movable sections in 2A,2B the vicinity of the driving electrodes 12C, 12D are attracted towardthe driving electrodes 12C, 12D by an electrostatic force, and thedriving electrodes 4, 8 on the side of the movable sections 2A, 2B areattracted to the driving electrodes 12C, 12D. It follows that the firstand second movable sections 2A, 2B are moved toward the glass plate 13.In this case, the first and second movable sections 2A, 2B are moved tothe right in FIG. 8A by a distance equal to two stripes of the drivingelectrode section 12, i.e., a distance equal to two pitches, comparedwith the position described in item (1) above.

(6) In the next step, the voltage of the driving electrodes 12C and 12Dis changed into a low level L at time t5, and a voltage is applied againto the holding electrodes sections 14A, 14B as shown in FIGS. 9E and 9F.It follows that a strong electrostatic force is generated between theholding electrode section 14A and the fixing electrode 5 on the side ofthe movable section 2A. As a result, the first movable section 2A ismoved toward the glass plate 15, and the fixing electrode 5 on the sideof the movable section 2A is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section 2B. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section 2B is attracted to the holding electrode section14B.

(7) In the next step, the voltage of the holding electrode sections 14A,14B is changed into a low level L at time t6, and a voltage H is appliedto the driving electrodes 12D and 12A as shown in FIGS. 9D and 9A. As aresult, the driving electrodes 4, 8 on the side of the movable sections2A, 2B in the vicinity of the driving electrodes 12D, 12A are attractedtoward the driving electrode stripes 12B, 12A by an electrostatic force,and the driving electrodes 4, 8 on the side of the movable sections 2A,2B are attracted to the driving electrodes 12D, 12A. It follows that thefirst and second movable sections 2A, 2B are moved toward the glassplate 13. In this case, the first and second movable sections 2A, 2B aremoved to the right in FIG. 8A by a distance equal to three stripes ofthe driving electrode section 12, i.e., a distance equal to threepitches, compared with the position described in item (1) above.

(8) In the next step, the voltage of the driving electrodes 12D, 12A ischanged into a low level L at time t7, and a voltage H is applied againto the holding electrodes sections 14A, 14B as shown in FIGS. 9E and 9F.It follows that a strong electrostatic force is generated between theholding electrode section 14A and the fixing electrode 5 on the side ofthe movable section 2A. As a result, the first movable section 2A ismoved toward the glass plate 15, and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section 2B. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section 2B is attracted to the holding electrode section14B.

(9) Further, the voltage of the holding electrode sections 14A, 14B ischanged into a low level L at time t8, and a voltage is applied again tothe driving electrodes 12A and 12B as shown in FIGS. 9A and 98. As aresult, the driving electrodes 4, 8 on the side of the movable sections2A, 2B in the vicinity of the driving electrodes 12A and 12B areattracted toward the driving electrodes 12A and 12B by an electrostaticforce, and the driving electrodes 4, 8 on the side of the movablesections 2A, 2B are attracted to the driving electrodes 12A and 12B. Itfollows that the first and second movable sections 2A, 28 are movedtoward the glass plate 13. In this case, the first and second movablesections 2A, 2B are moved to the right in FIG. 8A by a distance equal tofour pitches, compared with the position described in item (1) above.

The steps of items (1) to (9) described above are repeated so as to movethe first and second movable sections 2A, 2B by a desired distance.

(II) Where the first and second movable sections 2A, 2B are moved to theleft in FIG. 8A. the steps of operation mode I described above arecarried out in the opposite direction. To be more specific, the steps initems (9), (8), (7), (6), (5), (4), (3), (2) and (1) for operation modeI described above are carried out in the order mentioned so as to movethe first and second movable sections 2A, 2B to the left in FIG. 8A by adesired distance.

(III) Operation to move the second movable section 2B alone to the leftor to the right with the first movable section 2A held stationary.

Let us describe first the case where the second movable section 2B ismoved to the right as shown in FIG. 8B.

(1) In the first step, the driving electrodes 4, 8 of the movablesections 2A., 2B are held connected to the ground. Under this condition,a voltage is applied to the holding electrode section 14B as shown inFIG. 10F. As a result, an electrostatic force is generated between theholding electrode section 14B and the fixing electrode 5 on the side ofthe movable section. It follows that the second movable section 2B ismoved toward the glass plate 15, and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14B. In this case, the first movable section 2A is moved toward any ofthe glass plates 13, 15 and fixed temporarily. Where a voltage isapplied to the holding electrode section 14A as shown in FIG. 10E, thefirst movable section 2A is attracted to the glass plate 15 andcontinues to be fixed.

(2) In the next step, a voltage H is applied to the driving electrodes12A and 12B at time t1 as shown in FIGS. 10A and 10B, with the voltage Hkept applied to the holding electrode section 14A as shown in FIG. 10E.As a result, the driving electrode 8 on the side of the movable section2B in the vicinity of the driving electrodes 12A and 12B are attractedtoward the driving electrodes 12A and 12B by an electrostatic force, andthe driving electrode 8 on the side of the movable section 2B areattracted to the driving electrodes 12A and 12B. It follows that thesecond movable section 2B is moved toward the glass plate 13. On theother hand, since the voltage H is kept applied to the holding electrode14A, the first movable section 2A is kept fixed on the side of the glassplate 15.

(3) In the next step, a voltage H is applied to the holding electrode14B at time t2 as shown in FIG. 10F, with the voltage kept applied tothe holding electrode 14A. As a result, a strong electrostatic force isgenerated between the holding electrode 14B and the fixing electrode 11on the side of the movable section 2B. It follows that the secondmovable section 2B is moved toward the glass plate 15, and the fixingelectrode 11 on the side of the movable section 2B is attracted to theholding electrode 14B.

(4) In the next step, a voltage H is applied to the driving electrodes12B and 12C at time t3 as shown in FIGS. 10B and 10C, with the voltagekept applied to the holding electrode 14A. As a result, the drivingelectrode 8 on the side of the movable section 2B in the vicinity of thedriving electrodes 12B and 12C is attracted toward the drivingelectrodes 12B and 12C by an electrostatic force, with the result thatthe driving electrode 8 on the side of the movable section 2B isattracted to the driving electrodes 12B and 12C. It follows that thesecond movable section 2B is moved toward the glass plate 13. On theother hand, the first movable section 2A is similarly kept fixed on theside of the glass plate 15. In this case, the second movable section 2Bis moved to the right in FIG. 8B by a distance equal to one stripe ofthe driving electrode section 12, i.e., a distance equal to one pitch,compared with the position described in item (1) above.

(5) In the next step, a voltage H is applied to the holding electrode14B at time t4 as shown in FIG. 10F, with the voltage kept applied tothe holding electrode 14A. As a result, a strong electrostatic force isgenerated between the holding electrode 14B and the fixing electrode 11on the side of the movable section 2B. It follows that the secondmovable section 2B is moved toward the glass plate 15, and the fixingelectrode 11 on the side of the movable section 2B is attracted to theholding electrode section 14B.

(6) In the next step, a voltage is applied to the driving electrodes 12Celectrodes 12C and 12D at time t5 as shown in FIGS. 10C and 10D, withthe voltage kept applied to the holding electrode 14A. As a result, thedriving electrode 8 on the side of the movable section 2B in thevicinity of the driving electrodes 12C electrodes 12C and 12D isattracted toward the driving electrodes 12C by an electrostatic force,with the result that the driving electrode 8 on the side of the movablesection 2B is attracted to the driving electrodes 12C electrodes 12C and12D. It follows that the second movable section 2B is moved toward theglass plate 13. On the other hand, the first movable section 2A issimilarly kept fixed on the side of the glass plate 15. In this case,the second movable section 2B is moved to the right in FIG. 8B by adistance equal to two stripes of the driving electrode section 12, i.e.,a distance equal to two pitches, compared with the position described initem (1) above.

(7) In the next step, a voltage H is applied to the holding electrode14B at time t6 as shown in FIG. 10F, with the voltage kept applied tothe holding electrode 14A. As a result, a strong electrostatic force isgenerated between the holding electrode 14B and the fixing electrode 11on the side of the movable section 2B. It follows that the secondmovable section 2B is moved toward the glass plate 15, and the fixingelectrode 11 on the side of the movable section 2B is attracted to theholding electrode section 14B.

(8) In the next step, a voltage is applied to the driving electrodes 12Dand 12A at time t7 as shown in FIGS. 10D and 10A, with the voltage keptapplied to the holding electrode 14A. As a result, the driving electrode8 on the side of the movable section in the vicinity of the drivingelectrodes 12D and 12A is attracted toward the driving electrodes 12Dand 12A by an electrostatic force, with the result that the drivingelectrode 8 on the side of the movable section is attracted to thedriving electrodes 12D and 12A. It follows that the second movablesection 2B is moved toward the glass plate 13. On the other hand, thefirst movable section 2A is similarly kept fixed on the side of theglass plate 15. In this case, the second movable section 2B is moved tothe right in FIG. 8B by a distance equal to three stripes of the drivingelectrode section 12, i.e., a distance equal to three pitches, comparedwith the position described in item (1) above.

(9) In the next step, a voltage is applied to the holding electrode 14Bat time t8 as shown in FIG. 10F, with the voltage kept applied to theholding electrode section 14A. As a result, a strong electrostatic forceis generated between the holding electrode section 14B and the fixingelectrode 11 on the side of the movable section. It follows that thesecond movable section 2B is moved toward the glass plate 15, and thefixing electrode 11 on the side of the movable section is attracted tothe holding electrode section 14B.

(10) Further, a voltage is applied to the driving electrodes 12A and 12Bat time t9 as shown in FIGS. 10A and 10B, with the voltage kept appliedto the holding electrode 14A. As a result, the driving electrode 8 onthe side of the movable section in the vicinity of the drivingelectrodes 12A and 12B is attracted toward the driving electrodes 12Aand 12B by an electrostatic force, with the result that the drivingelectrode 8 on the side of the movable section is attracted to thedriving electrodes 12A and 12B. It follows that the second movablesection 2B is moved toward the glass plate 13. On the other hand, thefirst movable section 2A is similarly kept fixed on the side of theglass plate 15. In this case, the second movable section 2B is moved tothe right in FIG. 8B by a distance equal to four stripes of the drivingelectrode section 12, i.e., a distance equal to four pitches, comparedwith the position described in item (1) above.

The steps of items (1) to (10) described above are repeated so as tomove the second movable sections 2B by a desired distance.

Where it is desired to move the second movable section 28 to the rightkill, the steps of operation mode III described above are carried out inthe order of items (1), (10), (9), (8). (7), (6), (5), (4), (3) and (2)described above so as to move the second movable section 2B to the leftby a desired distance.

(IV) Operation to move the first movable section 2A alone to the left orto the right with the second movable section 2B held stationary.

Let us describe first the case where the first movable section 2A ismoved to the right as shown in FIG. 8C.

(1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are held connected to the ground. Under this condition,a voltage is applied to the holding electrode section 14A as shown inFIG. 11E. As a result, an electrostatic force is generated between theholding electrode section 14A and the fixing electrode 11 on the side ofthe movable section 2A. It follows that the first movable section 2A ismoved toward the glass plate 15, and the fixing electrode 5 on the sideof the movable section 2A is attracted to the holding electrode section14A. Where a voltage is applied to the holding electrode section 14B asshown in FIG. 11F, the second movable section 2B is attracted to theglass plate 15 and continues to be fixed.

(2) In the next step, a voltage H is applied to the driving electrodes12A and 12B at time t1 as shown in FIGS. 11A and 11B, with the voltage Hkept applied to the holding electrode section 14B as shown in FIG. 11F.As a result, the driving electrode 4 on the side of the movable section2A in the vicinity of the driving electrodes 12A and 12B is attractedtoward the driving electrodes 12A and 12B by an electrostatic force, andthe driving electrode 4 on the side of the movable section 2A isattracted to the driving electrodes 12A and 12B. It follows that thefirst movable section 2A is moved toward the glass plate 13. On theother hand, since the voltage H is kept applied to the holding electrode14B, the second movable section 2B is kept fixed on the side of theglass plate 15.

(3) In the next step, a voltage H is applied to the holding electrode14A at time t2 as shown in FIG. 1E, with the voltage kept applied to theholding electrode 14B. As a result, a strong electrostatic force isgenerated between the holding electrode 14A and the fixing electrode 5on the side of the movable section 2A. It follows that the first movablesection 2A is moved toward the glass plate 15, and the fixing electrode5 on the side of the movable section is attracted to the holdingelectrode 14A.

(4) In the next step, a voltage H is applied to the driving electrodes12B and 12C at time t3 as shown in FIGS. 11B and 11C, with the voltagekept applied to the holding electrode 14B. As a result, the drivingelectrode 4 on the side of the movable section 3A in the vicinity of thedriving electrodes 12B and 12C is attracted toward the drivingelectrodes 12B and 12C by an electrostatic force, with the result thatthe driving electrode 4 on the side of the movable section 2A isattracted to the driving electrodes 12B and 12C. It follows that thefirst movable section 2A is moved toward the glass plate 13. On theother hand, the second movable section 2B is similarly kept fixed on theside of the glass plate 15. In this case, the first movable section 2Ais moved to the right in FIG. 8C by a distance equal to one stripe ofthe driving electrode section 12, i.e., a distance equal to one pitch,compared with the position described in item (1) above.

(5) In the next step, a voltage H is applied to the holding electrode14A at time t4 as shown in FIG. 11E, with the voltage kept applied tothe holding electrode 14B. As a result, a strong electrostatic force isgenerated between the holding electrode 14A and the fixing electrode 5on the side of the movable section. It follows that the first movablesection 2A is moved toward the glass plate 15, and the fixing electrode5 on the side of the movable section 2A is attracted to the holdingelectrode section 14A.

(6) In the next step, a voltage H is applied to die driving electrodes12C electrodes 12C and 12D at time t5 as shown in FIGS. 11C and 11D,with the voltage H kept applied to the holding electrode 14B. As aresult, the driving electrode 4 on the side of the movable section 2A inthe vicinity of the driving electrode strip 2A, 2B is attracted towardthe driving electrodes 12C by an electrostatic force, with the resultthat the driving electrode 4 on the side of the movable section 2A isattracted to the driving electrodes 12C electrodes 12C and 12D. Itfollows that the first movable section 2A is moved toward the glassplate 13. On the other hand, the second movable section 2B is similarlykept fixed on the side of the glass plate 15. In this case, the firstmovable section 2A is moved to the right in FIG. 8A by a distance equalto two stripes of the driving electrode section 12, i.e., a distanceequal to two pitches, compared with the position described in item (1)above.

(7) In the next step, a voltage H is applied to the holding electrode14A at time t6 as shown in FIG. 1E, with the voltage H kept applied tothe holding electrode 14B. As a result, a strong electrostatic force isgenerated between the holding electrode 14A and the fixing electrode 5on the side of the movable section. It follows that the first movablesection 2A is moved toward the glass plate 15, and the fixing electrode5 on the side of the movable section is attracted to the holdingelectrode section 14A.

(8) In the next step, a voltage H is applied to the driving electrodes12D and 12A at time t7 as shown in FIGS. 11D and 11A, with the voltage Hkept applied to the holding electrode 14W As a result, the drivingelectrode 4 On the side of the movable section 2A in the vicinity of thedriving electrodes 12D and 12A is attracted toward the drivingelectrodes 12D and 12A by an electrostatic force, with the result thatthe driving electrode 4 on the side of the movable section is attractedto the driving electrodes 12D and 12A. It follows that the first movablesection 2A is moved toward the glass plate 13. On the other hand, thesecond movable section 2B is similarly kept fixed on the side of theglass plate 15. In this case, the first movable section 2A is moved tothe right in FIG. 8A by a distance equal to three stripes of the drivingelectrode section 12, i.e., distance equal to three pitches, comparedwith the position described in item (1) above.

(9) In the next step, a voltage H is applied to the holding electrode14A at time t8 as shown in FIG. 11E, with the voltage H kept applied tothe holding electrode 14B. As a result, a strong electrostatic force isgenerated between the holding electrode section 14A and the fixingelectrode 5 on the side of the movable section. It follows that thefirst movable section 2A is moved toward the glass plate 15, and thefixing electrode 5 on the side of the movable section is attracted tothe holding electrode section 14A.

(10) Further, a voltage H is applied to the driving electrodes 12A and12B at time t9 as shown in FIGS. 11A and 11B, with the voltage keptapplied to the holding electrode 14B. As a result, the driving electrode4 on the side of the movable section in the vicinity of the drivingelectrodes 12A and 12B is attracted toward the driving electrodes 12Aand 12B by an electrostatic force, with the result that the drivingelectrode 4 on the side of the movable section is attracted to thedriving electrodes 12A and 12B. It follows that the first movablesection 2A is moved toward the glass plate 13. On the other hand, thesecond movable section 2B is temporarily kept fixed on the side of theglass plate 15. In this case, the first movable section 2A is moved tothe right in FIG. 8C by a distance equal to four stripes of the drivingelectrode section 12, i.e., a distance equal to four pitches, comparedwith the position described in item (1) above.

The steps of items (1) to (10) described above are repeated so as tomove the first movable section 2A by a desired distance.

Where it is desired to move the first movable section 2A to the right,the steps of operation mode III described above are carried out in theorder of items (1), (10), (9), (8), (7). (6), (5), (4), (3) and (2)described above so as to move the first movable section 2A to the leftby a desired distance.

The relationship between the positions of the first and second movablesections 2A, 2B and the zooming magnification (magnification ofenlargement or reduction) of the lens system will now be described withreference to FIGS. 12A and 12B.

In general, a signal supplied by the user to the input section, e.g., abutton or a knob, of an apparatus such as a PDA mounted to theelectrostatic actuator is forwarded to a control unit 19 within theapparatus. The control signal for the zooming is formed in the controlunit 19 based on the input signal. The first and second movable sections2A, 2B are driven in accordance with the control signal.

FIG. 12A is a vertical cross sectional view showing an electrostaticactuator, and FIG. 12B is a graph showing the relationship between thepositions in the axial direction of the first and second movablesections 2A, 2B and the optical magnification. Curve P in FIG. 12Bdenotes the moving range of the first movable section 2A, and line Qdenotes the moving range of the second movable section 2B. As apparentfrom FIG. 12B, there is an overlapping region in the moving ranges ofthe first and second movable sections 2A and 2B in substantially thecentral portion of the stator 3. Incidentally, in the graph of FIG. 12B,the origin of the abscissa is set at one open portion of the stator 3 ofthe electrostatic actuator on the side of which the first movablesection 2A is mounted.

As shown in FIG. 12A, a CCD sensor 17 is arranged on a fixed plate 18 onthe image forming plane of the lenses 6 and 9 in the other open portionof the stator 3 on the side of which the second movable section 2B ismounted, and the fixed plate 18 is fixed to the other open portion ofthe stator 3.

Also, as shown in FIG. 12B, where the optical system is set at a certainoptical magnification X, the first movable section 2A is arranged in apoint E and the second movable section 2B is arranged in another pointF. Likewise, where the optical system is set at an optical magnificationY larger than the optical magnification X, the first movable section 2Ais set at a point G and the second movable section 2B is set at a pointH. Further, where the optical system is set at an optical magnificationZ larger than the optical magnification Y, the first movable section 2Ais set at a point I and the second movable section 2B is set at a pointJ.

Where the first and second movable sections 2A, 2B are moved to desiredpositions relative to a desired optical magnification, the first andsecond movable sections 2A, 2B are roughly moved first, followed byfixing one of the first and second movable sections 2A, 2B and finelymoving the other movable section, which is movable, so as to set theposition of the movable section, which is movable, at a desiredposition. Then, the movable section whose position has been set isfixed, and the other movable section is finely moved so as to be set ata desired position (fine operation).

The operations described above are performed by the steps describedpreviously in conjunction with the operation modes I to IV so as to moveindependently the first and second movable sections 2A and 2B, therebysetting the optical system at a desired magnification.

In the embodiment described above, the first and second movable sections2A, 2B are roughly moved first, followed by fixing one movable sectionand finely moving the other movable section so as to be set at a desiredposition, thereby setting the optical system at a desired opticalmagnification. Alternatively, it is also possible to move the first andsecond movable sections 2A, 2B directly to the desired positions byindependently controlling the first and second movable sections 2A, 2Bwithout fixing one of the first and second movable sections 2A, 2B inthe midway of setting the positions of these first and second movablesections 2A, 2B so as to obtain a desired optical magnification. Wherethe first movable section 2A is temporarily moved toward the drivingelectrode section 12 or is temporarily fixed on the side of the drivingelectrode section 12 in the particular operation, the second movablesection 2B is moved toward the holding electrode section 14B or istemporarily fixed to the holding electrode section 14B without fail. Inthe latter case, however, the time required for the magnification orreduction is rendered somewhat longer than that in the former case.

In the first embodiment described above, a plurality of movable sectionsfor magnifying or reducing the photographed image are independentlyoperated so as to obtain a desired optical magnification.

An electrostatic actuator according to a second embodiment of thepresent invention will now be described with reference to FIGS. 13A to13C.

In each of the embodiments described below, the same constituents of theelectrostatic actuator are denoted by the same reference numerals so asto avoid an overlapping description.

In the electrostatic actuator according to the second embodiment of thepresent invention, the holding electrodes 5, 11 on the side of themovable sections are formed in substantially the entire regions of thelower surfaces of the first and second movable sections 2A, 2B.

FIG. 13A is a side view schematically showing the movable sections ofthe electrostatic actuator according to the second embodiment of thepresent invention. FIG. 13B is a plan view schematically showing thelower surfaces of the movable sections shown in FIG. 13A. Further, FIG.13C is a plan view directed to the glass plate of the electrostaticactuator according to the second embodiment of the present invention andschematically showing the upper surface of the glass plate on which themovable sections shown in FIG. 13A are slid.

The fixing electrode 5 on the side of the movable section, which isshaped as shown in FIG. 13B, is mounted to the lower surface of thefirst movable section 2A shown in FIG. 13A. The fixing electrode 5 onthe side of the movable section extends planar on the lower surface ofthe first movable section 2A and is substantially in the form of a combhaving three projecting regions projecting toward the second movablesection 2B and two recessed regions sandwiched between the adjacentprojecting regions.

As shown in FIG. 13B, the fixing electrode 11 on the side of the movablesection is mounted to the lower surface of the second movable section2B. The fixing electrode 11 on the side of the movable section extendsplanar on the lower surface of the second movable section 2B and issubstantially in the form of a comb having three recessed regions on theside of the first movable section 2A and two projecting regionssandwiched between the adjacent recessed regions. As apparent from FIG.13B, the holding electrodes 5, 11 on the side of the movable sectionsare formed complementary such that the recessed regions of one of theseholding electrodes 5, 11 are engaged with the projecting regions of theother of these holding electrodes 5, 11.

As shown in FIG. 13C, the holding electrode sections 14A, 14B extendplanar such that these holding electrode sections 14B, 14B areelectrically separated from each other in the central portion of theglass plate 15 and are shaped in the central portion of the glass plate15 to conform with the shapes of the holding electrodes 5, 11 on theside of the movable sections, respectively. To be more specific, theholding electrode sections 14A, 14B are shaped complementary in thecentral portion of the glass plate 15 such that the recessed regions ofone of these holding electrode sections 14A, 14B are engaged with theprojecting regions of the other of these holding electrode sections 14A,14B. The electrostatic actuator of the particular construction isoperated in a manner similar to that of the electrostatic actuator shownin FIG. 4A. It should be noted, however, that the holding electrode 14Afor temporarily fixing the first movable section 2A on the side of theplate 15 is formed to extend to only about the central portion of theglass plate 15. Also, the holding electrode section 14B for temporarilyfixing the second movable section 2B on the side of the glass plate 15is formed in that region of the glass plate 15 in which the holdingelectrode section 14A is not formed in a manner to extend to only aboutthe central portion of the glass plate 15. It follows that the firstmovable section 2A is capable of movement from the open portion to onlyabout the central portion of the glass plate 15. Likewise, the secondmovable section 2B is capable of movement from the CCD sensor 17 to onlyabout the central portion of the glass plate 15.

It should also be noted that, during the period between the time whenthe movement of the first and second movable sections 2A, 2B is finishedand the time when the first and second movable sections 2A, 2B newlybegin to be moved, the first movable section 2A continues to betemporarily fixed to any of the driving electrode sections 12 and 14A,and the second movable section 2B continues to be temporarily fixed toany of the driving electrode sections 12 and 14B. Under the fixed state,an electric current is supplied from the internal power source so as topermit the first and second movable sections 2A, 2B to continue to befixed to the driving electrode sections even if the main power source ofthe apparatus having the electrostatic actuator mounted thereto isturned off.

As described above, in the electrostatic actuator according to thesecond embodiment of the present invention, a plurality of movablesections for magnifying or reducing the photographed image areindependently operated so as to obtain a desired optical magnification.

It should also be noted that the moving ranges of the first and secondmovable sections are smaller than those in the first embodimentdescribed previously. However, the possibility of the breakage caused bythe mutual contact of the first and second movable sections 2A, 2B canbe eliminated in the second embodiment of the present invention so as toimprove the reliability of the electrostatic actuator.

An electrostatic actuator according to a third embodiment of the presentinvention will now be described with reference to FIGS. 14A to 14C.

In the electrostatic actuator shown in FIG. 14B, each of the holdingelectrodes 5, 11 on the side of the movable sections is formed in theshape of a flat plate.

FIG. 14A is a side view schematically showing the movable sections inthe electrostatic actuator according to the third embodiment of thepresent invention. FIG. 14B is a plan view schematically showing thelower surfaces of the movable sections shown in FIG. 14A. Further, FIG.14C is a plan view schematically showing the upper surface of the glassplate included in the electrostatic actuator according to the thirdembodiment of the present invention.

As shown in the left side portion of FIG. 14B, the fixing electrode 5 onthe side of the movable section is formed in the shape of a flat plate.It should be noted, however, that the fixing electrode 5 on the side ofthe movable section has an area larger than at least half the area ofthe lower surface of the first movable section 2A and is formed not toextend over the entire region of the lower surface of the first movablesection 2A. For example, the fixing electrode 5 on the side of themovable section is arranged away from the movable section 2B in adeviated manner in a predetermined direction.

The fixing electrode 11 on the side of the movable section is formed inthe shape of a flat plate in the right portion of FIG. 14C. It should benoted, however, that the fixing electrode 11 on the side of the movablesection has an area larger than at least half the area of the lowersurface of the second movable section 2B and is formed not to extendover the entire region of the lower surface of the second movablesection 2B. For example, the fixing electrode 11 on the side of themovable section is formed away from the first movable section 2A in adeviated manner on the side opposite to the predetermined directionnoted above.

Further, the holding electrode sections 14A, 14B are formed to extendplanar as shown in FIG. 14C. In other words, the two planar holdingelectrode sections 14A, 14B are formed apart from each other on theglass plate 15. The areas of the rectangular holding electrode sections14A, 14B are set in accordance with the moving range (opticalmagnification) of each of the movable sections. It is possible for theseareas to be substantially equal to each other or different from eachother. Also, the holding electrode section 14A, for example, is arrangedon the glass plate 15 in a deviated manner in a predetermined direction,and the holding electrode section 14B is arranged on the glass plate 15in a deviated manner on the side opposite to the predetermined directednoted above.

The electrostatic actuator of the construction described above isoperated in substantially the same manner as that of the electrostaticactuator according to the first embodiment of the present invention.Also, the first and second movable sections 2A, 2B can be moved onlywithin the ranges in which the holding electrode sections 14A, 14B areformed as in the electrostatic actuator according to the secondembodiment of the present invention. It should also be noted that,during the period between the time when the movement of the first andsecond movable sections 2A, 2B is finished and the time when the firstand second movable sections 2A, 2B begin to be newly moved, the firstmovable section 2A continues to be temporarily fixed to any of thedriving electrode sections 12, 14A, and the second movable section 2Bcontinues to be temporarily fixed to any of the driving electrodesections 12, 14B. The fixed state continues to be maintained by theelectric current supplied from the internal power source even if themain power source of the apparatus having the electrostatic actuatormounted thereto is turned off.

In the electrostatic actuator of the construction described above, themovable sections for magnifying or reducing the photographed image aremoved independently so as to obtain a desired optical magnification.

Also, the moving ranges of the first and second movable sections 2A, 2Bare rendered smaller than those in the first embodiment of the presentinvention. However, the possibility of the breakage caused by the mutualcontact of the first and second movable sections 2A, 2B is eliminated soas to improve the reliability of the electrostatic actuator.

It should also be noted that each of the holding electrode sections 14A,14B is in the shape of a rectangular flat plate. This facilitates themanufacture of the holding electrode sections 14A, 14B so as tocontribute to the reduction in the manufacturing cost.

The methods of manufacturing the first and second movable sections 2A,2B and the stator 3 in each of the first to third embodiments describedabove will now be described with reference to FIGS. 15A to 19.

The method of manufacturing the stator 3 will be described first withreference to FIGS. 15A to 15C.

FIG. 15A is a plan view showing in a developed fashion the parts of themovable section. FIG. 15B is an oblique view showing the assembled stateof the movable section shown in FIG. 15A. FIG. 15C is a plan viewschematically showing the state that the parts of the movable sectionare mounted to a mold in the process of manufacturing a stator frame.Further, FIG. 15D is an oblique view schematically showing the movablesection manufactured through the step shown in FIG. 15C.

As shown in FIG. 15A, the parts of the first movable section 2A comprisea first flat plate 20 having the electrode 4 mounted thereto, a secondflat plate 21 having the electrode 5 mounted thereto, an arcuate firstconnecting member 22 for connecting the first flat plate 20 and thesecond flat plate 21 to each other, an arcuate second connecting member23, and an abutting member 24 attached to the first flat plate 20. Thedriving electrode 4 on the side of the movable section, which has aconcave-convex configuration, and the fixing electrode 5 on the side ofthe movable section is formed by etching on the surfaces of the firstflat plate 20 and the second flat plate 21, respectively. The first flatplate 20, the second flat plate 21, the first connecting members 22, 22,the second connecting members 23, 23, and the abutting member 24 areintegrally formed by a press molding from a metal plate.

The parts of the first movable section 2A are assembled by the foldingas shown in FIG. 15B. Specifically, the connecting portion between thefirst flat plate 20 and the first connecting members 22, 22, theconnecting portion between the second flat plate 21 and the firstconnecting members 22, 22, the connecting portion between the secondflat plate 21 and the second connecting members 23, 23, and theconnecting portion between the second connecting members 23, 23 and theabutting member 24 are folded such that the driving electrode 4 on theside of the movable section and the fixing electrode 5 on the side ofthe movable section are arranged on the outside. After the folding, theabutting member 24 is bonded to the first flat plate 20 by, for example,a spot welding. The first connecting members 22, 22 and the secondconnecting members 23, 23 are capable of elastically receiving thepressure from the outside, with the result that the movable section isconstructed flexible.

In the next step, the parts of the first movable section 2A are fixed bya resin as shown in FIG. 15C.

For fixing the first movable section 2A, used are molds 25A, 25B, 25Cand 25D, which can be separated into four parts. The convex portions ofthe driving electrode 4 on the side of the movable section and thefixing electrode 5 on the side of the movable section are allowed toabut against the inner surfaces of the molds 25A, 25B and, thus, concaverecessed spaces are formed on the inner surfaces of the molds 25A, 25B.The mold 25C is fixed in a sandwiched fashion between the molds 25A and25B. Convex portions in which the lens 6 having a stepped shape isfitted are formed in the outer surfaces of the mold 25C facing the innerwalls of the molds 25A, 25B. The mold 25D is also fixed in a sandwichedfashion between the molds 25A and 25B and positioned to face the mold25C. The mold 25D is arranged to abut against the mold 25C and to beapart from those regions of the first and second flat plates 20, 21 inwhich the driving electrode 4 on the side of the movable section and thefixing electrode 5 on the side of the movable section are not arranged.

In the first step, the molds 25A and 25B are arranged in contact withthe driving electrode 4 on the side of the movable section and theconvex portion of the fixing electrode 5 on the side of the movablesection of the first movable section 2A. Then, the molds 25C and 25D areinserted into the clearance between the molds 25A and 25B in a manner toclose the up-down direction of the first movable section 2A. As aresult, the first movable section 2A is covered with the molds 25A to25D. In this step, the first flat plate 20 and the second flat plate 21are urged against the molds 25A, 25B by the connecting members 22, 22,23, 23. The molds 25A to 25D are fixed so as not to be moved.

In the next step, a resin is introduced into the clearance through aresin-introducing hole 26 communicating with a part of the mold 25B. Inthis step, the molds 25A to 25D are maintained at about 150° C. by aheating means such as a heater, and the resin is poured into theclearance under a state maintained at about 300° C. After the pouring ofthe resin, the poured resin is gradually cooled with time to about roomtemperature so as to be solidified. By the solidification of the resin,the first movable section 2A is fixed without being moved by theconnecting members 22, 22, 23, 23.

It should be noted that, in this stage, the first and second flat plates20, 21 are urged by a predetermined elastic force against the molds 25A,25B, with the result that the first and second flat plates 20, 21 areheld apart from each other by a substantially predetermined distance. Asa result, the distance between the driving electrode 4 on the side ofthe movable section and the fixing electrode 5 on the side of themovable section of the first movable section 2A prepared by solidifyingthe resin is held substantially constant. In addition, the nonuniformityin the manufacturing accuracy can be eliminated so as to obtain aplurality of first movable sections 2A having substantially the sameshape.

As shown in FIG. 15D, the lens 6 is mounted to one surface in the axialdirection of the first movable section 2A.

Incidentally, the second movable section 2B can also be manufactured bya method similar to the method of manufacturing the first movablesection 2A described above.

The resin to be introduced into the clearance is preferably a materialhaving a conductive characteristics into which electrical conductiveparticles such as carbon particles are mixed to improve an reliabilityof the wiring on the movable sections 2A and 2B.

The manufacture of the stator frame 3 will now be described withreference to FIGS. 16A to 16C.

As shown in FIG. 16A, used are two separable molds 30A, 30B. Bores areformed in these molds 30A, 30B such that, when the molds 30A and 30B arecombined, the bores are allowed to conform with the outer configurationof the stator frame 3.

At the beginning, the molds 30A and 30B are in a separated state.

The glass plates 13, 15 each having a substantially U-shaped lateralcross section are arranged such that the back surfaces of the glassplates 13, 15 are brought into contact with the convex portions of apair of mutually facing surfaces 31A, 31B of the molds 30A, 30B,respectively. The patterned driving electrode section 12 and the holdingelectrode 14 are formed on the surfaces facing the back surfaces of theglass plates 13, 15 and arranged on the surfaces 31A, 31B of the molds30A, 30B, respectively, in a manner to permit the driving electrodesection 12 and the holding electrode section 14 to face each other. Itshould be noted that the glass plates 13, 15, in which the shapes ofthese electrodes are simplified, are shown in FIG. 16B.

The molds 30A and 30B are combined such that the side surfaces of aparallelepiped core 32 shown in FIG. 16D are in contact with a surface31C, not in contact with a surface 31D, and in contact with edges 33 ofthe driving electrode section 12 and the holding electrode section 14.When the molds 30A and 30B are combined, the concave portions of thedriving electrode section 12 and the holding electrode section 14 arenot in contact with the concave portions of the core 32, the surface 31Dand the surface 31C. Incidentally, the details in the shapes of themolds 30A and 30B are partly omitted in FIG. 16C.

It should also be noted that the core 32 is not in contact with surfaces34A, 34B, and 34D and is in contact with the convex portion of a surface34C.

A resin having a conductivity such as a resin is poured into theclearance between the core 32 and the surfaces 34A to 34D. In thisstage, the molds 30A, 30B are kept heated to about 150° C. by a heatingmeans such as a heater, and the resin is poured into the clearance in astate held at about 300° C. After the pouring, the resin is graduallycooled with time to about room temperature so as to be solidified.

The core 32 is taken out a predetermined time later (after completion ofsolidification of the resin), and the molds 30A and 30B are separatedfrom each other so as to obtain the stator 3 of a desired shape.

The electrostatic actuator is prepared by combining the first and secondmovable sections 2A, 2B, the stator 3 and the glass plates 13, 15 thusmanufactured.

Another method of manufacturing the movable section will now bedescribed with reference to FIGS. 17A to 17C.

As shown in FIG. 17A, the driving electrode 4 on the side of the movablesection is obtained by processing a silicon substrate. Theconcave-convex configuration of the driving electrode 4 on the side ofthe movable section is formed by an etching such that one surface of thesilicon substrate is allowed to bear a concave-convex configuration of adesired size, i.e., on the order of several microns. The etching methodis equal to the method employed for increasing the degree of integrationof an LSI. It is possible to employ any of the wet etching and the dryetching for forming the concave-convex configuration noted above.

As shown in FIG. 17B, a body 35 of the movable section is prepared byassembling a flat plate formed of a conductive resin into aparallelepiped state. The lens 6 is mounted in the axial direction ofthe body 35 of the movable section, and a pad 36 to which is connected aground wiring 7 connected to the ground is formed in a part of the sidesurface of the body 35 of the movable section.

As shown in FIG. 17C, the driving electrode 4 on the side of the movablesection thus prepared is bonded to the body 35 of the movable section,and the fixing electrode 5 is bonded to the upper surface of the body 35of the movable section with an acrylic adhesive that is cured uponirradiation with an ultraviolet light so as to prepare the first movablesection 2A.

An electrostatic actuator is manufactured by combining the first movablesection 2A thus manufactured and the stator 3.

The method of manufacturing the movable section will now be describedwith reference to FIG. 18.

FIG. 18 shows the method of manufacturing the movable section. As shownin the drawing, molds 37A to 37D are combined, and a resin is pouredinto the clearance among the molds 37A to 37D so as to manufacture thefirst movable section 2A. Incidentally, the mold 37D has a lengthreaching the mold 37C.

The resin poured into the clearance among the molds 37A to 37D isprepared by mixing carbon particles 38 with carbon fibers 39 each havingan electrical conductivity. Incidentally, the carbon particles 38 aresubstantially in the form of spheres each having a diameter of severalmicrons. On the other hand, the carbon fibers 39 are in the form of rodseach having a diameter of about 10 μm and a length of scores of microns.The first movable section 2A that is not provided with a lens isprepared by solidifying the particular resin.

According to the manufacturing method described above, the convex shapesof the driving electrode 4 on the side of the movable section and thefixing electrode 5 on the side of the movable section of the firstmovable section 2A are formed at an interval of about 20 μm. Therefore,it is possible for the carbon fiber 39 not to enter the clearancebetween adjacent convex portions 40, i.e., not to enter a concaveportion 41. However, even if the carbon fiber does not enter the concaveportion 41, the carbon particle 38 mixed in the resin enters the concaveportion 41. It follows that it is possible to obtain the first movablesection 2A having a good conductivity.

The movable sections 2A, 2B may be made of a nonconductive resin. Inthese movable sections 2A, 2B, an electrical conductivity can be appliedto the movable sections with plating a conductive film on the movablesections 2A, 2B after the molding. This method have a disadvantage ofincreasing manufacturing steps, but according to this manufacturingmethod, a good conductivity can be applied to the movable sections 2A,2B.

Another method of manufacturing the movable section and the stator willnow be described with reference to FIG. 19.

FIG. 19 shows the manufacturing method of the movable section and thestator. As shown in the drawing, the first and second movable sections2A, 2B and the stator 3 into which the first and second movable sections2A, 2B are inserted are formed in a single mold 42A. Incidentally, FIG.19 shows an example of the mold in which two stators and two movablesections are formed.

The shape of the mold of the first and second movable sections 2A, 2B issubstantially equal to that shown in FIG. 18. Also, the shape of themold of the stator 3 is substantially equal to that shown in FIG. 16A.The shapes of the driving electrode 4 on the side of the movable sectionand the fixing electrode 5 on the side of the movable section are formedon a pair of mutually facing inner surfaces 43A, 43B of the firstmovable section 2A. Also, the shapes of the driving electrode 12 and theholding electrode 14 are formed on a pair of mutually facing innersurfaces 44A, 44B of the mold of the stator 3.

By using the molds 42A, 42B of the particular construction, it ispossible to manufacture the first and second movable sections 2A, 2B andthe stator frame 3 low in the nonuniformity of the dimensional accuracyin a short time on the mass production basis.

Needless to say, the present invention is not limited to each of theembodiments described above and can be worked in variously modifiedfashions within the technical scope of the present invention. Forexample, it is possible to detect the positions of the two movablesections by an optical sensor and, if these two movable sections arelikely to collide against each other, it is possible to fix temporarilyone of these movable sections so as to avoid the collision.

Also, it is not absolutely necessary for two movable sections to beinserted into the stator. It is possible for three or more movablesections to be inserted into the stator in order to obtain a desiredmagnification.

Further, the shapes of the first bonding member and the second bondingmember are not particularly limited as far as these bonding members areshaped to produce elastic characteristics.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the present invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A method of driving an electrostatic actuator,the electrostatic actuator comprising: first stator electrodes arrangedin a predetermined direction and extending in a direction crossing thepredetermined direction; a second stator electrode arranged to face thefirst stator electrodes and extending in the predetermined direction; athird stator electrode arranged to face the first stator electrodes andextending in the predetermined direction so as to be electricallyisolated from the second stator electrode; a first movable sectionprovided with first movable section electrodes and a second movablesection electrode, the first movable section being configured to bemovable within a moving space in the predetermined direction, the movingspace being defined between the first stator electrodes and the secondstator electrode, the first movable section electrodes being mounted tothe first movable section to face the first stator electrodes and thesecond movable section electrode being mounted to the first movablesection to face the second stator electrode; and a second movablesection provided with third movable section electrodes and a fourthmovable section electrode, the second movable section being configuredto be movable within the moving space in the predetermined directionindependently of the first movable section, the third movable sectionelectrodes being mounted to the second movable section to face the firststator electrodes and the fourth movable section electrode being mountedto the second movable section to face the third stator electrode, themethod comprising: supplying first and second driving signals to thefirst and the second stator electrodes, respectively, to move the firstmovable section in the space in the predetermined direction, andsupplying a holding signal to the third stator electrode to hold thesecond movable section.
 2. The method according to claim 1, wherein thefirst stator electrodes, the first movable section electrodes, and thethird movable section electrodes are arranged substantially in parallel.3. The method according to claim 2, wherein the first movable sectionelectrodes and the third movable section electrodes have substantially asame arranging pitch and width.
 4. The method according to claim 2,wherein the first stator electrodes have an arranging pitchsubstantially equal to one-fourth of the arranging pitch of the firstmovable section electrodes and the third movable section electrodes. 5.The method according to claim 1, wherein the first movable section ismoved in the moving space in the predetermined direction with the fourthmovable section electrode being attracted to the third stator electrodeso as to hold the second movable section.
 6. A method of driving anelectrostatic actuator, the electrostatic actuator comprising: firststator electrodes arranged in a predetermined direction and extending ina direction crossing the predetermined direction; a second statorelectrode arranged to face the first stator electrodes and extending inthe predetermined direction; a third stator electrode arranged to facethe first stator electrodes and extending in the predetermined directionso as to be electrically isolated from the second stator electrode; afirst movable section provided with first and second movable sectionelectrodes and a second movable section electrode, the first movablesection being configured to be movable within a moving space in thepredetermined direction, the moving space being defined between thefirst stator electrodes and the second stator electrode, the firstmovable section electrodes being mounted to the first movable section toface the first stator electrodes and the second movable sectionelectrode being mounted to the first movable section to face the secondstator electrode; and a second movable section provided with thirdmovable section electrodes and a fourth movable section electrode, thesecond movable section being configured to be movable within the movingspace in the predetermined direction independently of the first movablesection, the third movable section electrodes being mounted to thesecond movable section to face the first stator electrodes and thefourth movable section electrode being mounted to the second movablesection to face the third stator electrode, the method comprising:supplying first and second driving signals to the first and secondstator electrodes, respectively, to move the second movable section inthe predetermined direction, and supplying a holding voltage signal tothe second stator electrode to hold the first movable section.
 7. Themethod according to claim 6, wherein the first stator electrodes, thefirst movable section electrodes, and the third movable sectionelectrodes are arranged substantially in parallel.
 8. The methodaccording to claim 7, wherein the first movable section electrodes andthe third movable section electrodes have substantially a same arrangingpitch and width.
 9. The method according to claim 7, wherein the firststator electrodes have an arranging pitch substantially equal toone-fourth of the arranging pitch of the first movable sectionelectrodes and the third movable section electrodes.
 10. The methodaccording to claim 6, wherein the second movable section is moved in themoving space in the predetermined direction with the second movablesection electrode being attracted to the second stator electrode so asto hold the first movable section.
 11. A method of driving anelectrostatic actuator, the electrostatic actuator comprising: firststator electrodes arranged in a predetermined direction and extending ina direction crossing the predetermined direction; a second statorelectrode arranged to face the first stator electrodes and extending inthe predetermined direction; a third stator electrode arranged to facethe first stator electrodes and extending in the predetermined directionso as to be electrically isolated from the second stator electrode; afirst movable section provided with first movable section electrodes anda second movable section electrode, the first movable section beingconfigured to be movable within a moving space in the predetermineddirection, the moving space being defined between the first statorelectrodes and the second stator electrode, the first movable sectionelectrodes being mounted to the first movable section to face the firststator electrodes and the second movable section electrode being mountedto the first movable section to face the second stator electrode; and asecond movable section provided with third movable section electrodesand a fourth movable section electrode, the second movable section beingconfigured to be movable within the moving space in the predetermineddirection independently of the first movable section, the third movablesection electrodes being mounted to the second movable section to facethe first stator electrodes and the fourth movable section electrodebeing mounted to the second movable section to face the third statorelectrode, the method comprising: supplying first and second drivingsignals to the first and second stator electrodes, respectively, to movethe first and second movable sections simultaneously in thepredetermined direction.
 12. The method according to claim 11, whereinthe first stator electrodes, the first movable section electrodes, andthe third movable section electrodes are arranged substantially inparallel.
 13. The method according to claim 12, wherein the firstmovable section electrodes and the third movable section electrodes havesubstantially a same arranging pitch and width.
 14. The method accordingto claim 12, wherein the first stator electrodes have an arranging pitchsubstantially equal to one-fourth of the arranging pitch of the firstmovable section electrodes and the third movable section electrodes. 15.A method of driving an electrostatic actuator, the electrostaticactuator comprising: a stator including a hollow stator frame having aspace extending in a predetermined direction, the hollow stator framehaving a first inner surface extending in parallel to the predetermineddirection and a second inner surface, wherein first stator electrodesare arranged in the predetermined direction on the first inner surfaceand each of the first stator electrodes extend in a direction crossingthe predetermined direction and second and third stator electrodes thatare electrically isolated from each other are arranged on the secondinner surface so as to extend in the predetermined direction; a firstmovable section arranged in the space to be movable in the space in thepredetermined direction, the first movable section including firstmovable section electrodes facing the first stator electrodes, each ofthe first movable section electrodes extending in the direction crossingthe predetermined direction and a second movable section electrodeextending in the predetermined direction to face the second statorelectrode; a second movable section arranged in the space to be movablein the space in the predetermined direction, the second movable sectionincluding third movable section electrodes facing the first statorelectrodes, each of the third movable section electrodes extending inthe direction crossing the predetermined direction and a fourth movablesection electrode extending in the predetermined direction to face thethird stator electrode, the method comprising: supplying first andsecond driving signals to the first and the second stator electrodes,respectively, to move the first movable section in the space in thepredetermined direction, and supplying a holding signal to the thirdstator electrode to hold the second movable section.
 16. The methodaccording to claim 15, wherein the first movable section is moved in thespace in the predetermined direction with the fourth movable sectionelectrode being attracted to the third stator electrode so as to holdthe second movable section.
 17. The method according to claim 15,wherein the second and third stator electrodes extend substantially inparallel in the predetermined direction and the second and fourthmovable section electrodes also extend substantially in parallel in thepredetermined direction.
 18. The method according to claim 15, whereinthe second and third stator electrodes are planar electrodes extendingin the predetermined direction and arranged separately from each otherin the predetermined direction and the first and second movable sectionsare moved within the range in which the second and third statorelectrodes are extended in the predetermined direction.
 19. A method ofdriving an electrostatic actuator, the electrostatic actuatorcomprising: a stator including a hollow stator frame having a spaceextending in a predetermined direction, the hollow stator frame having afirst inner surface extending in parallel to the predetermined directionand a second inner surface, first stator electrodes are arranged in thepredetermined direction on the first inner surface and each of the firststator electrodes extend in a direction crossing the predetermineddirection and second and third stator electrodes electrically isolatedfrom each other are arranged on the second inner surface so as to extendin the predetermined direction; a first movable section arranged in thespace to be movable in the space in the predetermined direction, thefirst movable section including first movable section electrodes facingthe first stator electrodes, each of the first movable sectionelectrodes extending in the direction crossing the predetermineddirection and a second movable section electrode extending in thepredetermined direction to face the second stator electrode; a secondmovable section arranged in the space to be movable in the space in thepredetermined direction, the second movable section including thirdmovable section electrodes facing the first stator electrodes, each ofthe third movable section electrodes extending in the direction crossingthe predetermined direction and a fourth movable section electrodeextending in the predetermined direction to face the third statorelectrode, the method comprising: supplying first and second drivingsignals to the first and the second stator electrodes, respectively, tomove the second movable section in the space in the predetermineddirection, and supplying a holding signal to the second stator electrodeto hold the first movable section.
 20. The method according to claim 19,wherein the second movable section is moved in the space in thepredetermined direction with the second movable section electrode beingattracted to the second stator electrode so as to hold the first movablesection.
 21. The method according to claim 19, wherein the second andthird stator electrodes extend substantially in parallel in thepredetermined direction and the second and fourth movable sectionelectrodes also extend substantially in parallel in the predetermineddirection.
 22. The method according to claim 21, wherein the second andthird stator electrodes are planar electrodes extending in thepredetermined direction and arranged separately from each other in thepredetermined direction and the first and second movable sections aremoved within the range in which the second and third stator electrodesare extended in the predetermined direction.
 23. A method of driving anelectrostatic actuator, the electrostatic actuator comprising: a statorincluding a hollow stator frame having a space extending in apredetermined direction, the hollow stator frame having a first innersurface extending in parallel to the predetermined direction and asecond inner surface, first stator electrodes are arranged in thepredetermined direction on the first inner surface and each of the firststator electrodes extend in a direction crossing the predetermineddirection and second and third stator electrodes electrically isolatedfrom each other are arranged on the second inner surface so as to extendin the predetermined direction; a first movable section arranged in thespace to be movable in the space in the predetermined direction, thefirst movable section including first movable section electrodes facingthe first stator electrodes, each of the first movable sectionelectrodes extending in the direction crossing the predetermineddirection and a second movable section electrode extending in thepredetermined direction to face the second stator electrode, a secondmovable section arranged in the space to be movable in the space in thepredetermined direction, the second movable section including thirdmovable section electrodes facing the first stator electrodes, each ofthe third movable section electrodes extending in the direction crossingthe predetermined direction and a fourth movable section electrodeextending in the predetermined direction to face the third statorelectrode, the method comprising: supplying first and second drivingsignals to the first and the second stator electrodes, respectively, tomove the first and the second movable section simultaneously in themoving space in the predetermined direction.
 24. The method according toclaim 23, wherein the second and third stator electrodes extendsubstantially in parallel in the predetermined direction and the secondand fourth movable section electrodes also extend substantially inparallel in the predetermined direction.
 25. The method according toclaim 23, wherein the second and third stator electrodes are planarelectrodes extending in the predetermined direction and arrangedseparately from each other in the predetermined direction and the firstand second movable sections are moved within the range in which thesecond and third stator electrodes are extended in the predetermineddirection.